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lVlire Spirov

FZ1

ulg

Mire Spirov

of Electrification

in Bulgaria

Electroimpex

HISTORY OF ELECTRIFICATION IN BULGARIA
Assoc. Prof. Mire Spirov, M.Sc. Electrical Engineer

ISBN 954-799-91 5-X

Written by Assoc. Prof. Mire Spirov, M.Sc. Electrical Engineer
Science editor Alexander Vaklinov, M.Sc. Electrical Engineer
Copy editors Mariana Dotsinska and Zlatka Barakova
Translation by Lyudmila Dimova
Art Direction by Ventseslav Dyankov

Graphic design by Ventseslav Dyankov ft Roumen Boboshevski

Prepress by Roumen Boboshevski

Photography Avram Avramov and Zhivko Arabov

Photo archival support by Electroimpex pic

Printed in Bulgaria by Obrazovanie ft Nauka

All rights reserved. No part of this book may be used or reproduced
in any manner, except brief quotations in critical articles or review,
without written permission of Electroimpex pic.
For further information, please write to:

Electroimpex pic

17, G. Washington Street, 1040 Sofia, BULGARIA

Tel: (+359 2) 86 181, Telex: 22959, Fax: (+359 2) 980 0272

E-mail: elimpex@mb.bia-bg.com

http://www.electroimpex.com

Foreword 5

Beginning and local electrification

1879-1918 6

Regional electrification

1919-1947.... 22

Interconnected electrification system -
overall electrification of the country

1948-1970 44

Introduction of new technologies
in electrification

1971-1991 64

Development of electrification
in the market economy

after 1991 78

Development of the electrical

equipment industry 84

Design and fulfillment
of electric power projects abroad -
ELECTR01MPEX and the Bulgarian
presence around the world 98

Appendix

104

Electrification is an essential part of the modern history of Bulgaria, starting with the first
electric bulb lit up in Sofia 1 20 years ago and the first tram introducing in the capital,
followed by many hydro and thermal power plants constructed through the years and
reaching the 1000 MW reactors of our first nuclear power plant in Kozloduy. Being the
backstone of our economy, the power sector has played a priority role in determining
the main economic tendencies in our country.

Regardless all economic shocks and difficulties arising from the accelerated introducing of
the market economy, the Bulgarian power sector has not been affected a lot, moreover it has
always given a stable support to our economy, even in the most difficult years. This is an
inevitable proof of the good professionalism and experience of the founders and creators
of our power system.

Electroimpex has also greatly contributed to the Bulgarian power sector, making it popular
abroad by the fulfillment of complete turnkey electric power projects and keeping the
Bulgarian "know-how" at a high competitive level.

By publishing this book, Electroimpex has the good will and intention to make the history
of Bulgarian Electrification more popular among our foreign partners. We have been led by
the good maximum: "One who knows History well, will become a master of the Future. One
who masters the Present, is a master of History, too". It is worth knowing the companies and
the people who have established and developed our electrification - from the very beginning
to the construction of the nuclear power plant in Kozloduy, the unique Chaira pumped
storage hydro power plant and the 750 kV overhead transmission lines on the territory of
Bulgaria, which for many countries is only a dream.

It was not by chance that we chose Assoc. Prof. Mire Spirov, M.Sc. Electrical Engineer, to
write this book. He is a famous Bulgarian expert, with a great experience in the studies,
design and development of the Bulgarian power sector, and also an established author of
a number of historical books about electrification.

We sincerely hope this book will give the readers a more detailed view to the Bulgarian
achievements in the field of electrification. It is a confirmation of the already proved trust
in the Bulgarian engineering companies and their reputation as reliable partners of world-
known foreign companies.

Alexander Vaklinov
Executive Director, Electroimpex

-■USES! iJ^KEEMEtoiaD' ' " '-'i Will i 1 "vi * Fff lP F tP H ir ff i ; l

lectrification, as an acquisition of material civiliza-
tion and culture, began in Bulgaria almost simul-
taneously with that in the developed European
countries - during the last two decades of the 19th century,
first by using electricity for lighting purposes only and
later on as a motive power.

The Royal Palace in Sofia

where the first electric bulb
in Bulgaria was lit up
(July 1st, 1879)

The fact that Bulgaria, recently liberated from Turkish
yoke (in 1878) took brave steps to introduce electric street
lighting in its capital city Sofia while Western Europe was
still fighting its way through lighting gas, is a significant
point in Bulgarian history. The high interest of Bulgarian
people in electric lighting could only be explained as a
continuation of the ideas of Bulgarian Renaissance.

So, on July 1st 1879, during the coronation ceremony of
Prince Alexander Batenberg-the first Bulgarian Royal
Prince of the Third Bulgarian Kingdom, the Royal Palace
was lit up with electric bulbs powered by electrical
installation supplied from Vienna. After 1885 electrical
lighting was also introduced in some other Bulgarian
towns, such as Gabrovo, Kazaniak, etc., as well as at the
Plovdiv Fair and at some other individual sites. In 1891
Ivan Hadjiberov's water-mill in Gabrovo was the first
to generate electricity from water power by means of
primitive facilities.

Table 1 presents the chronological order of the construction
of small individual electric power plants and facilities in
Bulgaria during the last decade of the 19th century, and
the capacity of each one.

Table 1 : Individual small power plants and facilities constructed in Bulgaria

during the period 1879-1901

Year of
commissioning

Royal Palace in Sofia (first electric bulb Lit up in Bulgaria)

"Uspeh" (Ferdinand 1st) Braiding Factory, Gabrovo

Rose Valley Wool Spinning Mill, Kazaniak

Hadjiberov's Water-Mill, Gabrovo

Hadjiberov's and An. Momarin's
Wool Weaving Workshop, Gabrovo

First Plovdiv Fair

Evksinograd Palace

Beer Brewery, Shoumen

Royal Palace in Sofia

Royal Stables in Sofia

Pernik Coal Mine

Anti-Plague Institute, Sofia

Parliament

Telegraph and Post Office Administration, Sofia

1879
1888
1889
1891

1892
1892
1893
1893
1895
1898
1999
1900
1900
1901

220
16
45
3

12.5
37.5

160
12.5
30

2.5
10
30

* The electric motors capacity is stated in hp (1 hp=0.735499 kW) for the period until 1948

The Sofia Palace Power Plant

commissioned in 1895

jront view

In 1 890 Dimitar Petkov, Mayor of Sofia at that time,

appointed a special "historical" commission that had to
carry out feasibility studies for the electric lighting of the
capital city. The commission worked out a program and
conditions for the factories wishing to participate in the
competition for lighting Sofia with electricity.

After a number of tenders had been carried out, a deci-
sion was made that the Pancharevo Hydro-Power Plant
on the Iskar river, 22 km away from Sofia, by the road to
Samokov, should be used as the first source of public
electricity supply to Sofia. The Belgian company Societe
d'Electricite de Sofia et de Bulgarie was a concessionaire
of the hydro-power plant, as well as of the transmission
and distribution network of the city.

The Iskar river was blocked by means of a stone masonry
dam with two steel gates in it, normally in horizontal
position, which rose to a vertical position in the event of
low water level, thus enabling daily compensation. On the
right-hand river bank, there was a draft gate, two vertical
shutters and a settling tank chamber, followed by an open
concrete culvert 149 m long, and then a 1167 m concrete
tunnel of 4.7 m 2 trapezoidal cross-section, with stone
lining. The tunnel ended in a water tower and steel pipeline
of 110 m length, d=1400 mm.

Pancharevo HPP

commissioned on
November 1st 1900
in operation until 1956

front view

The machine hall of the Pancharevo Hy<Lro-Power Plant
was 30 m wide and 12.5 m long, designed to accommo-
date 6 units. Initially, four units were installed. The tur-
bines were Francis type, made by Picaxd-Piete 8t Co.,
Geneva, with horizontal shaft of 500 hp capacity, 75%
efficiency and 400 rpm rotation speed, regulated by a
centrifugal governor. They were rated for 52-56 m head
and 960-910 1/s water discharge.

The generators were of an open type, connected to the
turbines by means of an open coupling. Their character-
istics were: 430 kVA capacity each, cos cp =0.8, voltage 8 kV,
frequency 53 Hz, exciter power-9 kW, 50V, 180 A.

Pancharevo HPP

Machine Hall

The construction of the Pancharevo Hydro-Power Plant,
as well as of the 22-km, 7 kV overhead transmission line
to Sofia and the city distribution network intended for
7 kV, 3kV and 150 V continued for two years pursuant to
the contract provisions. The installation works were per-
formed by the Swiss company Oerlicon.

The Pancharevo Hydro-Power Plant and the electric
power network of Sofia were commissioned on November
1st 1900 when the population of the capital city amount-
ed to 68 000. That was the beginning of public electricity
supply in Sofia and in Bulgaria.

Soon after electric lighting, the electric tram was intro-
duced in Sofia on January 1st 1901 by another Belgian
firm. And in 1902, the concessionaire commissioned
"Maria Louisa" back-up thermal power plant, near the
railway station, with two 600 hp steam engines, each
connected to a 450 kW, 7 kV synchronous generator and
each of them supplying one DC generator. Thus, the ther-
mal power plant could back up both the electric lighting
and the trams. It operated until the construction of the
Kourilo power plant (1927).

At the beginning of the 20th century (1901) the electric
lighting utility of Sofia had the following characteristics:

Installed capacity of the plant

2 000

7 kV overhead transmission
lines, 2x3x50 mm 2

16 025

Distribution network 7 and 3 kV

l_x X i_J l_ X X V_X i_ X V/ XX AX V. L V Y V/ 1 1 V I IX I X \JL -^J Jl V ¥

14 000

1 i V# V#

Low-voltage network 150 V

32 000

Distribution transformers 7000/150 V

pes

Distribution transformers 3000/150 V

pes

Street lamps

(according to the agreement terms,

ZZUU Ul3 WvlIC llll V 13d I^Cll, (JUL Ul WlllLfl

10 pes -16 A (approximately 500 W),
and 2000 pes -100 W filament lamps)

1 350

pes

Customers

249

pes

out of them private households

246

pes

motive power (palace, trams, a mill)

pes

Generated electric power

2 500 000

kWh

Sold electric power, including:

1 429 000

kWh

lighting of households

190 629

kWh

street lighting

651 573

kWh

motive power

3 066

kWh

electrical trams

584 090

kWh

Thus the young Bulgarian capital skipped the lighting gas
and the horse stage-coaches and equaled the developed
European countries in terms of electrification.

During the first five years of the development of electric
lighting in Sofia there was five-fold increase in consumers
and the total electric power consumption was almost dou-
bled. That on the one hand and the summer and winter
problems with the Iskar waters on the other hand made
the concessionaire expand the Maria Louisa power plant
in 1905 by a third, 600 hp steam engine, and in 1908-
by a fourth, 1000 hp steam engine.

In 1912 the first steam turbine in Bulgaria was installed
at the plant. It was a 2200 hp Brown Boveri steam turbine
completed with a 1500 kW Oerlicon generator.

In 1912 the electric power generated by the power plants
of Sofia reached the following figures:

❖ Pancharevo Hydro-Power Plant 5 721 802 kWh
♦> Maria Louisa Thermal Power Plant 1 252 905 kWh

TOTAL:

6 887 540 kWh

One of the first
Bulgarian books
on electrical
engineering, 19H

O6u4eAO3TmnH0 p^koboagtbo

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against 5 819 921 kWh demand, i.e. with 1 067 619 kWh
auxiliary consumption and transmission, transformation
and distribution losses, or 15 % of the power generated.
By that time the number of consumers had already
increased 20 times compared to 1901.

In 1915 the concessionaire, bearing in mind the rapid
increase of power demand, ordered a second, 2200 hp
unit from the same firms. However, its delivery was
delayed due to the breakout of World War I, so it was
installed in 1917.

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Hristo Lulev HPP

in Gabrovo

in operation since 1911

front view

Hristo Lulev HPP

Machine Hall

The electrification of Gabrovo was begun by Ivan

Hadjiberov-an enterprising factory owner, who was the
first in Bulgaria to produce electricity from water power.
In 1906 his own power plant on the Yantra river near
Gabrovo was commissioned. He had been personally
involved in its study, design and construction, This was
the second power plant for public electricity supply after
the Pancharevo HPP (1900), because besides the electric
power supply to the weaving workshop, it provided elec-
tricity to street lighting, as well.

The hydro-power plant had three water turbines with
installed capacity of 80 hp each. That permitted Ivan
Hadjiberov to expand the weaving workshop built by him
in 1912 by 80 new mechanical looms. His workshop had
already 300 workers and annual production of 180 000 m
woolen textile.

Even nowadays people are still amazed not only by the great
industrial interests Ivan Hadjiberov had, but also by his
extraordinary intellectual interests as evident from the pain-
tings on the power plant walls, the fascinating diary he kept
and the cultural acquisitions he provided for his workers.

The electrification needs of the industrial enterprises in
Gabrovo led to the construction of a new private hydro-
power plant "Hristo Lulev" on the Yantra river 14 km of
Gabrovo. It was commissioned in 1911. The plant had one
Francis turbine for 19.5 m water head and 1 m 3 /s water
flow, with a capacity of 135 kW and a generator for
6400 V three-phase current. The electric power was trans-
mitted to the town at 6 kV. Much later, in 1917, during
World War I, part of the electricity generated by Hristo
Lulev HPP was allocated for lighting of residential build-
ings in the town.

So, Gabrovo became the second town in Bulgaria to use
electric power in general, but as a town with public power
supply it took the fourth place after Sofia, Lorn and
Kazanlak.

Ivan Hadjiberov HPP

commissioned in 1 906
(the second HPP in Bulgaria
after Pancharero HPP)

front view

Lorn was a comparatively small town. However, as a port
on the Danube, at that time it was the gateway of Bulgaria
to Europe. The town electrification assigned by concession
to the German firm "Max Storh" started as early as 1907,
however, it was implemented as late as 1912. A diesel
power plant with two 150 hp generating sets was
constructed.

The generating sets were direct-current, for a three-wire
system, 100 kW, 440 V, 685 rpm, with belt drive. That was
a unique DC system in Bulgaria.

The DC generators were combined with two storage bat-
teries, always charged, which took over the electrical load
of the town, between 50 and 100 kW, for 7.5 hours when
the power plant did not operate. In this way the town
electrical lighting was maintained at nighttime in order to
economize on fuel which was rather expensive. Thus
Lorn, with its population of 15000 people, used storage
batteries for a period of 15 years-frorn 1912 to 1926.

The cooling water heated by the diesel engines was used
in the workers' bathroom, and the excess of hot water was
given to the town baths.

1st consumer
group

2nd consumer
group

S-self inductor

Fig, 1 I Lorn DPP-diagram of the 440/220 V DC three-wire system introduced in 1912

The Lorn Diesel Power Plant also supplied electricity to
the nearby village Golyantsi-the first electrified village
in Bulgaria ( 19 1 2). It is worth mentioning that this power
plant was also used, to a certain extent as a training
center for power plant electricians.

-J-

Beginning and local electrification 1879-1918

Enina HPP

commissioned on January 1st 1914

still in operation

Kazanlak was electrified by the joint-stock company
"Pobeda". It built a hydro-power plant on the Enina river
with the following characteristics:

❖ two 350 hp Pelton turbines;

❖ speed -7 50 rpm;

❖ water head- 101.9 m (gross);

❖ three-phase generators, 2x300 kVA, 750 rpm,
50 Hz, 6000-6500 V, cos cp= 0.8;

❖ turbine efficiency 85/87.3 % depending

on the load on the machines, i.e. 6-7% higher
than the efficiency guaranteed by Siemens.

The plant was commissioned in 1914. It was the first
electrification enterprise in Bulgaria built with Bulgarian
capital only, designed for public power supply to the town
and its industry. The electric power was transmitted from
the plant to the town through a 6 kV transmission line,
and the low-voltage distribution network was 220/127 V.

Nikola Batsarov ( 1 838- 1 890)

the first Bulgarian electrical engineer
graduated in 1887

The town of Varna -the "window" of Bulgaria to

the world, later on to become 'the seaside capital of
Bulgaria 1 , was among the first Bulgarian towns which
triumphantly received electric lighting in 1914, although
the first steps in that direction had been taken as early as
1900. A number of municipality mayors, decisions and
bids followed one after the other before the implementa-
tion of the project developed for the town electrification
by means of a diesel power plant. The bid was won
by Siemens-Schuckert. The diesel power plant had the
following characteristics:

♦> two diesel engines-270 hp, 187 rpm each;

❖ Siemens-Schuckert generators (1912), 187 rpm,
5 kV, directly connected to the respective
diesel engine, with 45 V exciter.

The high-voltage network (5 kV) used copper cables with
35 mm 2 phase cross section. Its total length was 8700 m.
Fourteen distribution transformers were installed in con-
crete construction, with two 40-50 kVA capacity each,
with dry insulation.

The low-voltage network (220/127 V) was a three-phase
type like that in Kazanlak. In 1912-1913, when the net-
work was constructed, Varna had a population of 43 000
people and 64 km total length of the streets 80°/o of
which, i.e. 48 km were electrified. The rest of the streets
were not yet covered by the town plan.

The Varna DPP (diesel power plant) was commissioned
on January 1st 1914, at the same time with the Enina HPP
commissioning. The utility belonged to the Varna
municipality.

The town of Rousse was electrified as late as 1917,

by the end of the period reviewed here. Since it was a
river-port town on the Danube and an important point on
the way to Western and Eastern Europe, as well as a cul-
tural center, the issue of its electrification was put forward
at the very beginning of the 20th century- A decision was
made for the setting up of a municipal electrification
enterprise. In 3911 there were already plans for the con-
struction of a diesel power plant and electricity distribu-
tion network in the town. A bid was announced for the
purpose and it was won by Siemens-Schuckert.

Beginning and local eletfriflcaticiB I8,j»19$i

Mil

Pursuant to the agreement terms and the bilateral con-
tract the firm Siemens- Schuckert supplied and installed
a diesel power plant with the following characteristics:

❖

3 generating sets with four-cylinder compressor
vertical diesel engines of 279 hp unit capacity, 187 rpm;

3 three-phase 260 kVA, 3000V, 50 Hz generators,
directly coupled to the engines and the respective
exciter.

The HV distribution cable network was for 3 kV voltage,
with section 3x50 mm 2 . Nine distribution transformers
for 3000/220/127 V were installed in metal construction.
The low-voltage network (210/120 V) was an overhead
three-phase type. The voltage applied to electrical motors
was 210 V, and for lighting purposes- 120 V.

Due to the wars Bulgaria was involved in during the second
decade of the 20th century, and World War I in particular,
the implementation of the Rousse power plant was greatly
delayed. It was officially commissioned in 1917.

For economic reasons, until 1921 the plant operated only
at nighttime, and after that -round the clock.

Table 2 presents a summary of the electrification enter-
prises for public power supply in Bulgaria by 1918.

Table 2: Electrification enterprises for public power supply in Bulgaria by 1918

Enterprise

Installed capacity of the plant, hp

Annual output
k Wh o/o

Concessions

3 720

7 580 -

11 300

78.55

1 1 000 000

89.34

Joint-stock companies

700

4.86

400 000

3.23

Private persons

467

3.24

350 000

2.84

Municipal

- 1 920

19 200

13.35

566 198

4.59

TOTAL :

4 887

7 580 1 920

14387

100.00

12316 198

100.00

Table 3

In 1918 the Belgian concession was far ahead of the other

electrical utilities both in installed capacity and electrici-
ty output-78.55% and 89.34% respectively.

Table 3 presents a comparison of investments by type of
enterprise.

Investments by 1

1918

Leva

o/o

Concessions

7 720 000

72.86

Joint-stock companies
Private persons
Municipal

460 000
300 000
2 114377

4.35
2.83
19.96

TOTAL:

10 594 377

100.00

Until the end of World War I (1918), although the Bulga-
rians were convinced of the usefulness of electrification
and that without it no significant progress in the country
was possible, most of the towns except for the above-
mentioned five ones, continued to use oil lamps for indoor
and street lighting (street lanterns).

During the period of local electrification eLectricity
demand level could be considered only in relation to sev-
eral electrified towns and villages, where, except in Sofia,
electricity was mainly used for lighting purposes. Sofia
had the highest specific electricity consumption per capi-
ta, as shown below:

Population of the city
Lighting, kWh per capita
Street lighting, kWh per capita
Motive power, kWh per capita
Trams, kWh per capita

102 812

14-

X 000

12.6

15.0

7.9

7.2

15.4

12.5

11.9

45.5

Before the end of World War I the average specific elec-
tricity consumption in Kazanlak for all purposes did not
exceed 45 kWh per capita, and in Varna it ranged
between 5 and 8 kWh per capita. This low figure was due
to the irregular operation of its diesel power plant.

The overall electricity generation in the country by 1913
(at the time of the Balkan wars) was estimated at about
110 million kWh and 2.2 kWh per capita on the average
for the country. At the same time the electricity con-
sumption per capita in the USA was 156 kWh, in
Germany-41 kWh, and in Russia-14 kWh.

That low electricity consumption corresponded to the low
specific installed capacity in the power plants- 50^-60 W
per capita, equal to the wattage of an electric lamp.
Correspondingly, the annual utilization ratio of installed
capacities in the power plants was low, although increas-
ing with time. For Sofia it was 670 h in 1901 and 1074 h
in 1917, and for Kazanlak -830 -1000 h, respectively.

It is worth noting that the electricity tariffs were quite
differentiated by consumer types and varied during that
period. In Sofia, for example, they were as shown below:

1902

1910 1916

Lighting, Leva/kWh

0.2350

0.3709

0.41

Motive power, Leva/kWh

0.0855

0.0967

0.18

Trams, Leva/kWh

0.0440

0.0973

0.09

More particularly, the price of electricity for household
lighting was 0.70 Leva/kWh. For Kazanlak the electricity
price in 1915 was 0.60 Leva/kWh, or three times higher
than the price of bread (0.20 Leva/kg). That price of elec-
tricity was very high bearing in mind that the workers'
wages at that time were 1.6-2 Leva (for female workers
they were 0.7-0.8 Leva).

The transition from local to regional electrification
in Bulgaria resulted from tracing out the general
lines of its development after World War 1. For the
purpose, a number of acts and plans were developed, the
more important of which included:

❖ Water Syndicate Act and General State Program for
Waters (1920);

❖ Commission with the Ministry of Agriculture and
State Property set up to work out a General
Electrification Plan of Bulgaria (1929-1933);

❖ Decree on the Electrification of Bulgaria (1935);

❖ Competition for the General Conceptual Design for the
Electrification of Bulgaria announced by the Ministry
of Public Buildings, Roads and Public Utilities (1940)
which resulted in a final, approved General
Conceptual Electrification Plan of Bulgaria in 1941;

❖ Two-year Plan of National Economy Electrification
(1946-1947).

Construction of large power plants, overhead transmission
lines and distribution substations was typical of the region-
al electrification during that period. Its development was
related to two main things: larger investments and better
organized steps for the General Plan implementation.

Table 4: Relative investments for power plants in Bulgaria

The State
Municipalities

Water syndicates and cooperatives
Popular banks

Joint-stock companies and private persons

8.36
11.5

14.47
4.81

60.86

7.66
24.39
30.10

4.90
32.95

32.40
36.20
6.40
4.20
20.80

63.80
13.85
4.82
5.18
12.35

TOTAL

100.00

1 00.00

100.00

However, both directions faced significant obstacles,
since at that time electrification services were distributed
among three ministries: Ministry of Commerce, Industry
and Labor; Ministry of Public Buildings, Roads and Public
Utilities; Ministry of Agriculture and State Property. The
lack of coordination among them, as well as the narrow
departmental interests impeded electrification to a great
extent. Moreover, initially private capital had the largest
share in the construction of power plants.

The Union of Bulgarian Engineers and Architects con-
tributed greatly to the leading of a correct and unified
state electrification policy by developing a proper devel-
opment strategy in that field.

The electrification regions in Bulgaria in the 1930's and
1940's were determined in conformity with the existing
administrative regions, as follows: Sofia, Plovdiv, Stara
Zagora, Bourgas, Varna, Rousse, Pleven, Vratsa and
Gorna Jumaya (Blagoevgrad).

Kourilo TPP

commissioned in 1927

front view

The electrification of the Sofia Region developed at the
highest rate due to the availability of hydro-power and
coal resources. After World War I, there was a huge influx
of refugees from the enslaved Bulgarian lands
(Macedonia, Thracia, Western Regions), a large part of
whom settled down in Sofia. The Belgian concessionaire
had to build "Kourilo" thermal power plant-within
12 km of Sofia [1927] for providing new electrical capacity

for the capital city. Initially, 2x6400 kW units were
installed, and then in 1930- a third unit, so the overall
plant capacity reached 19 200 kW. The plant was con-
nected to Sofia through 35 kV overhead transmission
lines. Unfortunately, the boiler capacity of the plant was
insufficient, so it could hardly reach 14 500 kW. Small-
sized (6-15 mm] brown coal from Pernik was used as fuel.

The capacity and electric power generated by the Kourilo
TPP supplemented the hydro-power plants of the compa-
ny and Sofia municipality, that is why Kourilo had low
annual utilization ratio which did not exceed 1000 h. The
Kourilo Plant, as well as Pancharevo HPP operated at 53 Hz
frequency till the commissioning of Mala Tserkva HPP
in 1934 when they switched over to a standard 50 Hz
frequency.

Water Tower

Kalin Dam

Kara Giol Dam

0.00 02000

Lower Chamber

Kalin HPP

Debrashtitsa Canal

L=1554 m t 2%
(p= 700 mm

Wooden Low Head Canal
L=21 49.88 m, 0=600/450 mm

Low Head Cana
L=902 m, 0=2400 mm
with 2600 m tunnel

Low Head Derivation
L=6000m. ^=2200 mm
with 19 tunnels of a tcta
length = 2969.5 m

Rila HPP

Fig. 2". Elevation diagram of the Rila Cascade

Construction

of the reinforced concrete
rectangular section
gutter to the Pastra HPP

A significant electric power source in that electrification
region was formed by the hydro-power plants of the Rila
Cascade owned by Granitoid J.S.C.: Pastra, 5520 kW
(1925); Rila, 6400 kW (1929); Kamenitsa, 33 75 kW (1940)
and Kalin, 4500 kW (1948). The electric power generated
in these plants was transmitted to Sofia and its electrifi-
cation region at 60 kV.

Rila HPP

commissioned in 1929

front view

In 1926 a new 60/15 kV distribution substation -"Orion",
was built in the north-west part of the capital city. By it
Granitoid set the beginning of regional, electrification
in Bulgaria.

Reinforced concrete

round section

gutter to the Rila HPP

Fig. 3: Plan of Granitoid IS. C.

transmission lines, 1934

For the purposes of water supply to the capital city, in
1933 the Rila Aqueduct was built, starting from the Rila
Mountain (the highest peak of which is 2925 m), with
three hydro-power plants erected along it: Simeonovo,
6280 kW (1927, 1934); Mala Tsarkva, 4200 kW (1934),
and Beli Iskar, 7700 kW (1957). The electric power from
the first two plants was transmitted to Sofia at 35 kV, and
from Beli Iskar -at 110 kV.

Petri ch

KOURILO

Chelopechene

Novoseltsi

Past r a HPP
Pastra HPP

60000/5000 V transformer
Steam turbines
Transformer 15 000/380/220 V
60 000 V overhead transmission line
15000 V overhead transmission line
5000 V overhead transmission line
35000 V overhead transmission line

Pirin Mines

Kroupnik

■

f-!

Perm* TPP

commissioned in 1929

front view

. 7. uidtSf* i

The Pernik State Mines were the third large electrification
enterprise in South-East Bulgaria. The needs of the mines
consumption and the region demand were met by the con-
struction of 6O00V Pernik TPP with 2x4000 kW units,
commissioned in 1929 . Using cheap waste brown coaL, the
plant was designed to reach 50 000 kW in the future.

1 5fOA kYA Distriimtioi Transformer

belonging to Granitoid
built during the 1930's

Pernik TPP

Batanovtsi
60/15/5-4 MVA

KouriloTPP
Veslets

35/7-3x7.5 MVA

Serdika

35/7-6x3 MVA

Rila

35/7-2.5 MVA

HPP
TPP

Substation

Two-wire 60 kV overhead transmission line
Single-wire 60 kV overhead transmission line
Two-wire 35 kV overhead transmission line
Single-wire 35 kV overhead transmission line
Two-wire 15 kV overhead transmission line
Single-wire 1 5 kV overhead transmission line

Samokov

Botevgrad

Mala Tsarkva HPP

M25

Vitinya

Rila HPP

Kamenitsa HPP

Pastra HPP

Fig. 4: Electrification plan of Southwest Bulgaria by 1944, diagram

60/35/15 kV Orion Substation

in operation since 192 6

(photo 1927)

■

Fig. 5: Development of Granitoid electricity consumption 1925-1943

The specific electricity consumption in the Sofia Region
in 1943 was as follows: in Sofia and the Tillages annexed
to it- 167 kWh per capita, and in the rest of the region-
121.8 kWh per capita at average specific electricity
consumption in Bulgaria 45 kWh per capita.

12 000

1966 '67 '68 '69 70 71 72 73 74 75 76 77 78 79 '80 '81 '82 '83 '84 '85 '86 '87 '88 '89 '90

Year

Fig. 6 1 Gross electricity consumption in the Sofia Electrification Region

Reconstruction of the 35 kV Pastra-Orion

overhead transmission line to 60 W
under tension, 192 9

1.13%

Plants in Sofia

Granitoid J.S.C.

Pernik Mines

Other Plants

17.36%

27.75 0/o

53.76%

Fig. 7: Allocation of the electricity

consumption in the Sofia
Electrification Region, 1943

Plovdiv Electrification Region

The Plovdiv Electrification Region was formed and built
exclusively by the Vacha Power Plant Water Syndicate. It
was the largest water syndicate in Bulgaria where consider-
able state capital was invested at the very beginning (1920).

The machines of Vacha HPP (later on called HPP Krichim)
were supplied by Alstom, France: 2x3500 kW, 6.2 kV,
directly coupled to the turbines. The water diversion tunnel
was 4754 m long, with 3 m diameter and throughput
capacity 5000 1/s. The plant was commissioned in 1933,
after a 10-year period of construction.

Due to the delayed completion of the Vacha HPP, in 1927
a thermal power plant with two 850 kW units with gen-
erator voltage of 2 kV was built in Plovdiv.

Prior to the construction of the Plovdiv TPP- property of
the Water Syndicate, some small power plants had been
used for public power supply in several towns in that
region, including: Plovdiv, Peshtera, KarLovo, Tiigrad,
Chepelare. Only Karlovo HPP was an exception with
capacity of its turbines 1x1500 hp and 1x490 hp.

The Vacha Water Syndicate also built 60 kV overhead
transmission lines from Krichim to Plovdiv and from
Krichim to Pazardjik, total length of 45 km, as well as
60/15 kV substations in Plovdiv and Pazardjik (1927).
The same syndicate built a large 15 kV distribution
network the length of which reached 1071 km in 1939, as
well as 780 km low-voltage network, and 394 distribution

The old Vacha HPP

commissioned in 1934

transformers -15/0.4 kV, with a total capacity of 21 703 kVA.
At that time the number of consumers reached 29 326,
1 5 658 of which were members of the Syndicate.

Dozens of various enterprises in the light and food-pro-
cessing industry, as well as hundreds of irrigation pump
stations in the fertile fields around Plovdiv and Pazardjik
were supplied with electricity.

Stara Zagora Electrification Region

During the first three decades of the 20th century ten
small individual power plants were built in Stara Zagora-
the center of that electrification region. Some of them also
supplied electricity for street and residential lighting.

It was only in 1930 when Svetlina Co. Ltd. was established.
On the basis of various options studied, it electrified the
town by means of the Vulkan TPP (located in the village
of Chernokonyovo, nowadays a suburb of Dimitrovgrad)
through a 35 kV overhead transmission line and a 35/6 kV
substation. In 1933 Stara Zagora had a population of
30 000 people and the electric load at the nine 6/0.4 kV
distribution transformers was equal to 380 kW, 240 kW
of which were used for residential lighting, 20 kW for
street lighting, and 120 kW as motive power.

At the beginning of the forties Stara Zagora, respectively its
35/6 kV substation, was connected to the regional Maritsa I
Power Plant (nowadays in Dimitrovgrad), and the electrici-
ty supply from the Vulkan company was terminated.

In order to meet the growing demand of Kazanlak which
had been electrified as early as 1914 by electricity supply
from the Enina HPP, in 1924 Pobeda constructed a diesel
power plant with 200 hp engine and 175 kVA, 6300 V gen-
erator. Five years later, in 1929, a second, more powerful
diesel unit with 400 hp engine and 350 kW, 6300 V
generator were installed. And in 1937 a third unit with a
780 kW, 6300 V generator was installed at the Enina HPP.

The other big towns in the region were electrified by small
diesel power plants not exceeding 500-600 kW capacity,
as follows: Sliven (1928), Yambol (1928), Nova Zagora
(1929), Haskovo (1934), Chirpan (1937), Kardjali (1939),
and a number of other towns and villages.

€f; % # $ ?§ W W % % W II '%

Bourgas Electrification Region

The electrification of Bourgas-the regional center, started in
1918 with the installing of one steam engine and a 100 kW
dynamo at the sea port. After that some more small electri-
cal facilities were installed. Much later, in 1927, the town
was electrified by means of the thermal power plant of the
Cherno More Mine owned by the Budeshte J.S.C. through
an 11 km, 15 kV overhead transmission line and a 15/6 kV
substation. In general, at that time, according to the instruc-
tions of the Ministry of Public Buildings, Roads and Public
Utilities, the distribution voltage in a town could not exceed
6 kV. A new joint-stock company "Adree" was established as
a daughter company of Budeshte J.S.C. for supplying
Bourgas with electricity.

At that time the Adree power plant had one unit of 750 kW.
In 1932 and 1937 it was extended by a second 200O kW unit
and a third 4000 kW unit respectively, all of them for 3 kV, as
well as its step-up substation 3/15 kV.

Later on, in 1946 a 20 kV overhead transmission line
"Adree-Straldja" was constructed, and Straldja nodal plant,
on its part, was power supplied from the 50/20 kV Yambol
Substation.

A few smaller power plants were built in the Bourgas electri-
fication region, the installed capacities of which did not
exceed 500 kW. They supplied power to some factories, as well
as generated electricity for the public power supply system.

In general, the length of the 3-20 kV electric lines in the
region a minor part of which were cable lines, was as follows:
in 1936-188 km, in 1944-298 km, and by 1950-756 km.
3-20/0.4 kV distribution transformers were connected to
these electric lines, the number and capacity of which were
as follows: in 1944-99 distribution transformers of 8660 kVA;
in 1950-223 distribution transformers of 18725 kVA. In the
period examined here no 60 kV overhead transmission lines
were built in the Bourgas Electrification Region.

The other towns in that region were electrified as follows:
Aitos (1930), Kamobat (1930), Pomorie (1931), Sozopol [1931),
Nessebar (1932), Michurin (1932). The first electrified village
was Aheloy (1936). Before 1944, 22 settlements were electri-
fied in that region- towns and villages, the fetter after 1940.

Varna Electrification Region

After the end of World War I the electricity supply in Varna
gradually returned to normal. Varna DPP (diesel power
plant) operated from 7.00 till 12.00 at daytime and from
sunset till midnight. Due to the small loads, only one ma-
chine ran in the morning, and both machines -at nighttime.

In 1922 the number of consumers amounted to 1873 with
electric meters and 1730 without electric meters, or a total
of 3603 consumers at town population of 43 000. These
figures show that a large part of the population in Varna
was not yet electrified -a situation typical of other electrified
towns in Bulgaria. In 1930 a municipal lighting business
enterprise was established in Varna. And in 1937 two small
separate power plants were also commissioned -one on the
Aqueduct from the Batova river, and the other at "Prince
Boris" Factory, with a total capacity of 500 kW.

Varna DPP

commissioned in 1914

front view

The electrical load increased quite rapidly, and in the
evenings the generators voltage fell from 5000 V to 4500 V
for covering the peak load. At the same time, the redemp-
tion time of the loan drawn by the enterprise for the first
three diesel generators was prolonged -the debt to the
bank amounted to 1 414 637 Leva and it was returned as
late as 1949.

Varna DPP

Machine Hall

A fourth diesel generator set was also supplied, but its
capacity was quite small -500 kW. The disputes whether
a new thermal power plant should be constructed or elec-
tricity should be supplied by Adree J.S.C.-Bourgas, went
on. A special commission assigned to carry out thorough
investigations, presented 3 options of development of
Varna electricity supply, as follows:

I. Extension of the existing DPP;

II. Supply of electricity from Adree-Bourgas, through
a 95 km 60 kV overhead transmission line;

III. Construction of a local thermal power plant.

The third option was recommended and approved.
Through a tender procedure, at the first stage a 2200 kW
unit was procured from Czechoslovashki Colben-Danek,
Prague (1944), and after that- a second 5000 kW unit,
so the total capacity became 7200 kW (10 000
The Varna DPP became a large regional power plant for
its time, in compliance with the decisions of the first gen-
eral electrification plan of 1941,

The Varna Municipality received a loan from the Electri-
fication Fund covering 30% of the resources initially
needed for the construction of a new thermal power
plant. Against that loan, the Municipality undertook the
obligation to electrify six districts including the newly
liberated Dobrudja (1940).

The civil works on the regional 20 kV overhead transmis-
sion lines to the value of 80 million Leva continued
simultaneously with the Varna DPP construction. Their
length reached 500 km, and sixty five 20/0.4 kV distribution
transformers to the cost of 50 million Leva were connected
to them.

Thus, by the end of World War II, the Varna electrifica-
tion region recovered and almost all towns were electri-
fied, but electric lighting still had to reach the villages.

Shoumen Electrification Region
including Rousse Region

Rousse was the only town in the Shoumen electrification
region electrified before World War I (1917). Another
exception was Silistra which was electrified in 1936 by
means of a DC diesel power plant, when Dobrudja was
still under Romanian rule.

The growing electricity consumption in Rousse required

■

that the Rousse diesel power plant should be extended by
a new diesel unit- a 600 hp engine from the Graz factory,
and a 470 kW Siemens generator (1926). So, the plant
reached 940 kW total installed capacity, and the town's
demand for electricity was completely met.

■

In 1936 a business enterprise -"Rousse Electricity Supply",
with its own budget was established. The Ministry of
Public Utilities assigned to it the electrification of other
towns in that region. For the purpose, in 1941 a thermal
power plant with one 2000 hp turbine and a 1400 kW
generator was built on the site of the Rousse DPP. Some
Rousse DPP small industrial and local power plants with capacity not

commissioned in 1917 exceeding a few hundreds of kilowatts were also used.

front view

Quite an early electrification was carried out in Razgrad
in 1930 by the construction of a 130 kW diesel power
plant and later, in 1933 a 350 kW extension to it. Koubrat
was also electrified in 1930, the village of Shtraklevo in
1933, etc.

Shoumen, as the main town in the region, was electrified
by means of a 270 hp diesel power plant with a 180 kW,
6000 V generator, and five 6/0.4 kV distribution trans-
formers (1927). So, 34 years after the first electric bulb was
lit up in Shoumen (at the brewery in 1893), the beginning
of electrification in the town was laid. Later on, the
Shoumen DPP was extended by a second 240 kW unit
(in 1929) and a third unit with a Wechsel engine, operating
as both diesel and gasogen engine (1939). The war time
when there was a shortage of diesel fuel necessitated the use
of such an engine that could operate using charcoal gas. For
the purpose, during the next few years (1942) the enterprise
bought 500 dca of forests in the mountains around Preslav
for the production of about 1 800 000 kgf charcoal.

With a view to regional electrification, the General
Directorate of Electrification in Bulgaria with the Ministry
of Electrification, Waters and Natural Resources com-
pleted the construction of a 20 kV overhead transmission
line: Varna-Pro vadia-Shoumen, thus in 1947 the two
power plants were connected for electric power exchange.

Besides the electrification of towns and villages in the
region, one of the high-priority objectives of the Shoumen
electricity supply enterprise was the electrification of the
water-supply pump stations in the dry ludogorie region
and in whole Dobrudja-9 districts as a whoLe by that
time. By 1944, 85 settlements of the 157 planned were
supplied with water.

Gorna Oryahovitsa
Electrification Region

The Gorna Oryahovitsa Electrification Region was formed
around a centre situated at the Gorna Oryahovitsa rail-
way junction due to its geographical and infrastructure
conditions. In that fertile and active region, a leading role
in electrification was played by Gabrovo where a signifi-
cant textile industry was developed at the beginning of
the 20th century by followers of Racho the Blacksmith
and Ivan Hadjiberov.

Regional electrification 1919-1947

Several water syndicates (WS) were set up in that region:
Malusha (1922), Gramadata (1926), Rositsa (1921), Yantra
(1921), as well as joint-stock companies and cooperatives
(Bedek, Videlina), and a dozen of industrial enterprises
that intended to meet their own electricity demand, as
well as to provide public power supply. The leading role
in that respect belonged to Gramadata WS-Gabrovo.
In 1926 it built a reliable diesel power plant of the same
name with initial generator capacity of 166 kW, 6kV, thus
laying the beginning of the overall public power supply
in Gabrovo. Only a few years later, a new 450 hp diesel
engine was supplied to Gramadata DPP.

Several other electrical utilities were also built in the
region: Malusha HPP with two units, 420 hp and 160 hp
(1940], Batoshevo 1 HPP on the Rositsa river, 625 kW
(1926], and Bedek TPP in Tryavna with unit capacities
600 kW (1931) and 2000 kW (1935), as well as a 60 kV
overhead transmission line to Maritsa East 1 and 60/20 kV
Gabrovo Substation (1945).

Gorna Oryahovitsa Substation

60/20 kV switchyard (1941)

Pleven Electrification Region

The Pleven Electrification Region was developed much
later, during the 1940's when the North Bulgaria
Electrification Directorate was established in 1940 and
transformed into General Directorate of Electrification in
Bulgaria on May 8th 1944.

In Pleven, the administrative center of the region, the
issue of electric lighting was raised in 1906, then in 1907
and again in 1911 (a project was drawn up), however,
electrification there was begun in 1919. At that time
a dynamo installed in a mill was also used for supplying
electricity lighting to the neighboring houses.

Large-scale electrification in Pleven began in 1927 when
the Pleven DPP was constructed and commissioned with
two diesel-engine units of 200 hp each. The Plant was
extended by 460 hp in 1930 and 1200 hp in 1949. It oper-
ated at 6 kV. The same was the town distribution voltage
and that of the 6/0.4 kV distribution transformers.

Later on (1950-1951) near the Pleven-West lailway plant,
a 110/20 kV regional substation was built in order to pro-
vide connection to the regional electrification system of
the country. That set the beginning of an orderly devel-
opment of the Pleven Electrification Region,

1 10/29 kV

Distribution Substation '
Chervtn Bryog-

the 20 kV indoor switchgear

under c onstruction

It is worth noting that near Loukovit, on the Zlatna Panega
river, the first dam in Bulgaria was built. It was given the
name of the river and had 1.2 million m 3 storage capaci-
ty and a power plant on it, with two units of 480 kW total
capacity, commissioned in 1938.

Mezdra Electrification Region

In the beginning the Mezdra Electrification Region devel-
oped as part of the Pleven Electrification Region. Mezdra
became a regional center owing to its geographical situ-
ation and position as a railway junction. As early as 1909
a small diesel engine was installed in the railway depot to
drive a dynamo for electric lighting of the railway plant
(until 1928). The town was electrified by means of a small
local plant in 1927, and from 1935 on it already had the
Rosa hydro-power plant on the Iskar river, connected to the
Sofia electrification system through a 20 kV overhead trans-
mission line and 15/20 kV autotransformer (1947).

The first 110 kV overhead transmission line in Bulgaria
was laid between Kourilo and Mezdra. It was designed
in 1942 by the Czech ex-Skoda Works -Pilzen and con-
structed by the same firm. Due to the political events in
Bulgaria the construction was stopped after 1944 and the
transmission line was completed by Bulgarian specialists
in the summer of 1949. Initially it operated at 35 kV.
In 1947 the first 110 kV substation in Bulgaria was
built- 110/20 kV Mezdra Substation. Initially it received
35 kV current from the Kourilo power plant. Later on in
1950 the substation, with one 5000 kVA autotransformer,
was set in parallel with the Sofia system through the
110 kV overhead transmission line. At the same time,
voltage was supplied to the 110 kV overhead transmission
line from Mezdra to Cherven Bryag-the second sector
of the 110 kV overhead transmission line ring pursuant to
the General Plan.

A number of 20 kV overhead transmission lines stretched
from the Mezdra substation and thus the Mezdra electri-
fication region was formed (1947). The towns that had
been earlier electrified through local power plants, such
as: Montana (Ferdinand, 1936), Vratsa (1927), Lorn
(1912), Byala Slatina (1929), Kozloduy (1933), at that time
were united into an interconnected 20 kV system.

Vidin

Rousse

Koubrat

aid"

\ lt\".

Vranya

Skopje

Treska

Veles

Brusartsi

Oryahovo

Pleven

Popovo

Razgrad

Levski

Pi rot

Sadovets
Cherven Bryag

Mezdra Gabrovo

Vit

Shoumen

Kourilo

S. Oryahovitsa
Tryavna

Orion

Pernik

ioyan;

Kalin

Rila

jskar Station gQ ^

Pancharevo
St. Peter

Muhovo

^ Pazardjik D , .
JVI. Tsarkv3^r7| plovd

B. Iskar

Tvarditsa

Tr °Y an HW Kazanlak Q

Nova Zagora Yambol 1

Kazanlak

Stara Zagora

Yambol

Pastrau Lakes Ribn ' Eli Dere

Simitli fl Vacha

Chaya

Mareeno

Tash boaz

St. Vratch

Kavadartsi

Ka rdj a I i

Provadia
Asparuchovo

Bourgas

Xanti

Seres

110 kV

Ohrid

Kavala

Gyumurdjina

Hydro- power plant
Steam-engine power plant
Substation 110/20 kV and 60/20 tV
Two-wire 110 kV overhead transmission line
Single 110 kV overhead transmission line
Two- wire 60 k\/ overhead transmission line
Single 60 kV overhead transmission line
Overhead transmission line built after 1960

fiijV-ViVuV;

Fig. 8: Electrification system diagram according to the First General Conceptual Electrification Plan

of Bulgaria (within the Bulgarian borders at that time), 1941

During the 1940's-the years of World War II (1939-1945)
significant large-scale changes occurred in Bulgaria con-
nected with its economic, state and political development,
including electrification.

In 1945 Bulgaria had 119 public utility power plants with
a total installed capacity of 110 968 kW and electric power
output of 401 261 000 kWh, or 57.8 kWh per capita on
the average. 94 of all these power plants had less than
1000 kW capacity; 56.8 % of their capacity consisted of
state and public power plants.

Before the end of 1947, seventeen 35-60/15-20 kV sub-
stations were installed with total capacity of 86.4 MVA.
The 60 kV transmission lines had a total Length of 480 km,
and the 35 kV transmission lines -166 km. In 1950 an
interconnection transmission line with Romania-
"Rousse-Giurgiu" was commissioned. It consisted of a 60 kV
cable line across the Danube.

There was a wide variety of medium distribution volt-
ages -3, 5, 6, 7, 15 and 20 kV. This led to the same variety
of the distribution transformers network. Their low voltage
was a three-phase one, 380/220V everywhere, and only in
Rousse, Varna and Kazanlak it was 210/110 V, and in Sofia-
150 V, three-phase one for AC without neutral tapping.

By 1947, 2724 distribution transformers of total installed
capacity of 269 545 kVA were built in Bulgaria, or 100 kVA
per distribution transformer on the average. The length of
the low-voltage network was 13 116 km or 4.81 km/per
distribution transformer.

In 1946 a new electrification authority was established -
the Ministry of Electrification, Waters and Natural
Resources which put an end to the lack of coordination
between the electrification services. The same Ministry,
and the General Directorate of Electrification in Bulgaria,
in particular, developed a two-year electrification plan
(1946-1947) involving an intense construction in that
area. An Energy Syndicate of all electrification enterprises
was also established making no difference between the
forms of ownership.

The increasing demand for engineers led to the opening
of a Higher Technical School in Sofia in 1942, with a
Faculty of Architecture and Civil Engineering which was
transformed into State Polytechnic (State Technical
University) in 1945. At that time the number of M.Sc.
electrical engineers was about 500 (1946).

The Union of Bulgarian Engineers and
Architects contributed a great deal to the deve-
lopment of all bills on the electrification of
Bulgaria, as well as to the opening of the Higher
Technical School and to the establishment in
1932 of the Bulgarian National Committee of
Energy with the World Committee of Energy
created in 1924.

Interconnected electrification system-Overall electrification of trie Country 1948-1 97C

3.1. Generating Capacities

he 23-year period examined herein was marked by a
campaign of the communist regime established in
Bulgaria after 1944. The acts, decrees and ordi-
nances adopted at that time brought about radical changes
in all spheres of life in the country. The most important
among them are:

1. Act on Industry, Bank and Mine Nationalization
and Electrification (24.12.1947);

2. Cooperation of Agricultural Lands and Establishment
of Agricultural Cooperatives (CLAC);

3. Giving priority to heavy and energy- intensive
industries;

4. Adoption of a special Electrical Industry Act in con-
nection with the Nationalization Act which came into
effect on January 1st 1948. The new act superseded the
act issued by the General Directorate of Electrification
in Bulgaria as well as the Acts of the Elprom Syndicate,
the Water Syndicates, the Acts on construction of the
Rositsa and Topolnitsa Dams, and the Act on Heat and
Electricity Supply Joint Ventures. On January 1st 1948
the Ministry of Electrification, Waters and Natural
Resources was transformed into two ministries:
Ministry of Electrification and Amelioration (MEA),
and Ministry of Mines and Mineral Resources (MMMR).

«tff ill*

iff ro irr mr (ft nrr fir

f|| fff $ m ik for S Iff ST BF RT

fff

Sofia TPP

commissioned in 1 949

(the first heating
plant in Bulgaria)
front view

Sofia-East TPP

commissioned in 1964

front view

5. A Decree of the Council of Ministers of 02.04.1948
led to the establishment of enterprises with the
Ministry of Electrification and Amelioration:

• Energoobedinenie-a state economic group for elec-
tric power generation, transmission and distribution,
including the power plants and electrification regions
each one as a separate accounting unit.

• Elprom-a state economic group encompassing all
enterprises in the field of electrical industry.

• Energostroy-a state enterprise for erection, upgrad-
ing and development of power plants, transmission
and distribution networks.

• Energohydroproject- state designer s bureau special-
ized in working out designs for any electrical or ame-
lioration projects.

6. Constant administrative changes, including the elec-
trification sector, as well, aiming to appoint political-
ly convenient non-professionals at high posts.

All these major changes affected, to one extent or anoth-
er, the development of electrification and, most of all, the
nationalization of electrification. At the same time we
should not neglect the fact that the Bulgarian electrical
engineers welcomed the nationalization of electrification
because for many years they had championed this kind of
electrification finding it as the only feasible form for its
accelerated development.

Five-year plans were worked out for a total development
of the Bulgarian economy. In respect to the electrification
projects, their terms were always fulfilled on time.

A specialized Science Research Institute of Electrification
and Electrical Industry was established in 1954.

The fast development of the electrical projects construc-
tion resulted in early completion of the target projects
under the 1941 General Conceptual Electrification Plan.
Thus Energohydroproject developed a Second General
Plan approved in 1955. It applied to a short term period
(1962); however, further on it underwent a number of
updates to meet longer term goals.

h:\vMon jm$&a ic I voMi f ic anon sv s

Overall electrification of tftt C o u at ry 1 94B % 1 970

After the nationalization of electrification, the first larger
public-utility thermal power plants (TPP) were construc-
ted, as well as power plants meeting the needs of some
individual industrial works. Table 5 presents the technical
data of these first power plants.

Table 5: Thermal power plants constructed during the period 1948 -1970

L DISTRICT HEATING PLANTS
Nadezhda (Sofia)

Republica (Peinik)
Sofia -East
Sliven

II. PUBLIC-UTILITY POWER PLANTS

Maiitsa-3 (D imitrovgrad)
Maritsa East-1

Rousse-East

Maritsa East- 2

Year of
com miss
ionin

Installed
capacity
MW

1st stage

Extension

Varna

1949

2x6

161

1 x 12

3 x 25

1 x 50

1952

2 x 25

100

1964

4 x 30

1 x 66

186

1969

1 x 30

1954

2 x 25

1 x 120

170

1960

4 x 50

2 x 1 50

500

1964

2 x 30

2 x 110

400

2 x 60

1966

4 x 1 50

2 x 210

1 450

2 x 215

1969

3 x 210

1 260

325 m flue

The fuel basis of the district heating plants was gas and
fuel oil (Nadezhda and Sofia-East), and brown coal
(Republica and Sliven), and that of the power plants was
lignite coal; only Varna TPP used imported steam coal
and gas, and Rousse TPP- imported steam coal only.

The largest thermal power plants in Bulgaria were built in
the Maritsa East lignite field, including Maritsa East 2 -the
largest thermal power plant on the Balkan Peninsula, with
the highest flue stack in Europe (325 m).

By the end of the 1950's there were wide discussions
about the priority development of thermal power plants
after a number of hydro-power plants and cascades had
already been built or studied for construction.

Passarel HPP

commissioned in 1956
overall view

Kokalyane HPP

commissioned in 1956

overall view

However, the smaller investments needed for thermal
power plants, in spite of their higher annual costs com-
pared to hydro-power plants, gave a green light to their
construction.

The building of large industrial works and industrial
complexes necessitated the construction of a number of
industrial thermal power plants with installed capacities
not exceeding a few tens of megawatts. These were:
Gorna Oryahovitsa TPP, 2x6 MW (1961); Kremikovtsi TPP,
3x25 MW, 50 MW and 12 MW (1963); Neftochim TPP-
Bourgas, 25 MW, 12 MW, 60 MW (1964); Devnya TPP,
5 units of total capacity 22 MW (1954); thermal power
plant of the Stara Zagora Nitrate Fertilizer Works, 4x6
MW (1963); thermal power plant of the Petrochemical
Works Plama-Pleven, 60 MW (1969); thermal power
plant of the Chemical Works-Vidin, 2x25 MW (1969);
Sviloza TPP-Svishtov, 2x60 MW (1970); Chimco
TPP-Vratsa, 2x25 MW, as well as a number of other
small thermal power plants belonging to some factories.

Bulgaria is quite deficient in hydro -power resources.
Moreover, these resources are unevenly distributed over
its territory. The technically utilizable hydro-power
potential of the country at that time amounted to 15 bil-
lion kWh, or about 1700 kWh per capita, and the cost
effective -to about 10 billion kWh.

With respect to water run-off, the country was divided into
three catchment areas with different energy potential:
Aegean (66.2%), Danubian (30.1%), and Black Se* (3.6%).

In 1949 -at the very beginning of the period reviewed
here, a special hydro-engineering and hydro-power con-
struction authority was established. It constructed sepa-
rate hydro-power plants, hydro-power systems, and com-
plete hydro-power cascades. At the same time the
Installation Works Authority with its subdivisions carried
out the installation of the power plants. That was already
a complete cycle of work of the Bulgarian experts.

Table 6 presents the technical indices of all hydro-power
cascades, respectively of the separate hydro- power plants,
as well as the year of their commissioning. Within a few
years of such construction and installation works the
Bulgarian specialists accumulated considerable experi-
ence which was applied later on in projects abroad.

Interconnected >1 ectrffica tio n system-Overall electrification of the Country 1

Table 6: Hydro-Power Cascades

Storage Com mis-

capacity sioned in
m 3 year

Units

Capacity Output

, , ,

ni 3 /s pes. —

mln.KWh

Petrohan Cascade

Klisoura HPP

Barzia HPP

Petrohan HPP

Iskar Cascade

Sircieonovo HPP

Mala Tserkva HPP

Beli Mar HPP

Pasard HPP

Kokalyane HPP

Batak Cascade

Batak HPP

Peshtera HPP

Aleko HPP

Arda Cascade

Kardjali HPP

Studen Kladenets HPP

Ivailovgrad HPP

Sandanska Bistritsa Cascade

598

378

1 O C*3

i ybJ

11 r a

I lb 4

z r o.b

1 C

I b

OCA 1 O

zbu 2,o

z r b.b

1957

509 1 .9

2P 7.8

1956

1928

456 2.1

3P 6.3

1934

300 3.5

3P 7.7

1956

355 6

2P 16

1956

103 33

2F 33

1956

92.5 30

2F 22.4

1959

400 1 3.6

4P 40

162

1959

580 26

5P 125

444

1959

265 30

3F 63

205

864

0.2

1963

80.5 162.4

1958

59.5 120

1965

44 270

Popina Laka HPP

- 1969

540

4.8

Lilyanovo HPP

- 1969

372

6.7

Sandanski HPP

— 1969

236

7.2

Pirinska Bistritsa Cascade
Pirin HPP
Spanchevo HPP
Dospat-Vacha Cascade
Teshel HPP
Devin HPP
Antonivanovtsi
Pumped-Stoiage HPP
Krichim HPP
Vacha-New HPP
Vacha-Old HPP
Belmeken-Sestrimo Cascade
Belmeken-Sestrimo
Pumped-Storage HPP
Sestrimo HPP
Momina Klisoura HPP
Chaira Pumped Storage Plant

0.1

652

1972
1984

141.5

1974
1974
1974

468
415

315
138

690
534
251

5.7
7.8

2P
2P

26
72

2F
2F

106
60

108
21.5
20
14.2

21
28

60
80

62.5
56.6
56.6

1995-99 640/660 144/118

5P
2P
2F
4

375/380
240
120

864/760

165
217
217

71
70
48

70
95

166
120

1975 111.8 168

160/40

245/58*

1972 162 61

198

1972 82 9.2

21.3

1934 83.2 20

21.6

556/220*
421
204
1200

•>:-•>:•

electric power generated by pumped storage hydro-power plant
P = Pelton, F = Francis, K = Kaplan

ARDA Hydro-Power Cascade

commissioned 1956-1965

Kardjali HPP

Stud en Kladenets Dam

Studen Kladenets HPP

Machine Hall

Ivailovgrad Dam

with hydro-power plant

Table 7 presents the development of the installed capa-
city in the Bulgarian power plants (luring the period
reviewed here.

Table 7: Installed capacity of power plants in Bulgaria 1944-1970 in MW

1944
1945
1950
1955
1960
1965
1970

130.5
126.7
175.7
482.1
925.5
2 127.5
4 083.5

Electrification administration

130.5
126.7
175.7

390.3
874.3
1 913.3
3 456.8

TPP HPP

plants

46.5

17.3 —

46.5

13.5 -

65.3

13.9 —

133.4

33.3 41.8

475.7

36.4 51.2

768.4

33.£ 214.2

811.7

30.4 B26.7

Interconnected electrification system -0 vera! 1 elec trifica t:i o n of t he Co u n t ry 194 8-1970

— .

—

Legend

DPP

Industrial plants

HPP
TPP

Total

- —

— i —

— — — —

4 400

4 200

4 000

3 800

3 600

3 400

3 200

3 000

2 800

2 600

2 400

2 200

2 000

1 800

1 600

1 400

1 200

1 000

800

600

400

200

1944 '45

'57

'69

Fig. 9:

Development of the installed capacities of thermal,

hydro- and diesel power plants

and industrial power plants, 1944-1971

H E S T O R Y of electrification in Bulgaria

7 000 -

6 000

5 000

CX3
<U

4 000

3 000

2 000 -

1 000

1950 '51 '52 '53 '54 '55 '56 *57 '58 '59

'63 '64 '65 '66 '67 '68 '69 70

Year

Fig. 10: Annual utilization ratio of the electrification authority power plants

These figures show that for a period of 2 5 years the total
installed capacity of the power plants had increased
32 times which was really a quite rapid development.
Electric power generation developed at the same rate,
thermal power plants contributing the largest share of it-
63% in 1950 and 72.6% in 1970. At the same time the
share of industrial power plants considerably increased
and at the end of the period it reached 16.2% of the
power generated (Table 8).

■:>■■

Regional electrification 1919-1941

Table 8 : Electric power generated in Bulgaria, kWh x 10 6

rification

plants

1953

505.9

267.5 23.6

797.0

797

1955

1 258.1

644.0 38.5

1 940.6

132.4

2 073

196D

2 441.8

1 883.9 167.8

4 493.5

163.5

4 657

1965

S 754.0

1 998.6 148.0

8 900.6

1 347.4

10 248

1973

14 177.0

2 152.2 10.8

16 340.0

3 174.8

19 515

9.7 o/o

Lignite coal

Imported coal

Fuel oil

Brown coal

43°/o

Fig. 11:

Power plants of the electrification authority
(not including industrial power plants)
grouped by type of fue

The annual utilization ratio of the plants belonging to the
electrification administration in the period 1950-1970
tended to decrease, its highest value was T = 5870 h in
1955, while for TPP that utilization ratio reached 7209 h
(1960) which was a very high value.

The auxiliary electricity consumption of the power plants
;rew over the years and its highest value reached 10.94 °/o
in 1969. At the thermal power plants alone it reached
12.79%, as for the hydro-power plants, it was 0.31% of
the power generated.

The specific fuel equivalent consumption for thermal
power plants varied between 540 and 405 g fuel equiva-
lent/^ Wh. In the reviewed period 1950-1970 the pay-roll
staff employment ratio in the electrification authority
power plants (not including industrial plants) was signi-
ficantly reduced from 5.57 employees /MW in 1950 to
1.83 employees/MW in 1970. For the thermal power
plants alone that ratio was 8.81 employees/MW and
2.06 employees/MW respectively.

All these technical and economic indices of electricity
;eneration sources show their major improvement in the
course of time.

21 000

20 000

19 000

18 000

1 7 000

16000

1 5 000

14000

13 000

1 2 000

11 000

10 000

9 000

8 000

7 000

6 000

5 000

4 000

3 000

2 000

1 000

944 '45 '47 '49 '51 '53 '55 '57 '59 '61

63 '65 '67 '69 '71

Fig. 1 2 1 Electric power generated in Bulgaria

by power plant types in the period 1944-1971

Fig. 11 illustrates the allocation of the generated electric
power among power plants of the electrification authori-
ty, without industrial plants, according to type of fuel.
It shows that the local resources (lignite and brown coal)
supported 51.4% of the electricity generated, while the
other resources were imported.

3.2. Transmission and Distribution Networks

The overall electrification network of the country, includ-
ing the electric power transmission system, developed on
the basis of the General Conceptual Electrification Plan of
1941 and the Second General Plan of 1955 and its
updates. Energoproject worked out separate general long-
term plans (until 1980) for the distribution networks of
the different electrification regions and towns (in a per-
spective until 1980).

Until the end of the 1950's the transmission system-
overhead transmission lines (OHTL) and transformer sub-
stations, was developed for 110 kV voltage. The 110 kV
overhead transmission lines ring was completed in 1958.
The 220 kV transmission voltage was introduced in 1959
through the transmission line from Aleko Substation to
Gorna Oryahovitsa Substation. Similar to the 110 kV
system, the "closed-loop" pattern was adopted. It was
mainly the 220 kV transmission system that developed
during the reviewed period.

Initially, the 110 kV overhead transmission lines were
supported by vibrated concrete poles and reinforced con-
crete cross arms on them. Reinforced-concrete structures
were also used in the 110/20 kV substations with outdoor
110 kV switchyards. Soon after that, however, that prac-
tice was abandoned and both the poles and the substa-
tions intended for such a voltage were replaced by steel
lattice towers for the overhead transmission lines and
steel lattice structures for the substations.

220/7 W kV Sofia South Substation

commissioned in 1975

Steel lattice structures are generally used for 220 kV
overhead transmission lines and for 220 kV and 110 kV
outdoor switchyards of the 220/110 kV substations. On
the basis of statistical laboratory tests, Energoproject
developed up-to-date designs of suspension and tension
towers for that voltage.

Initially the 110 kV transmission lines used copper con-
ductors (M-95 and M-120 mm 2 ), but later (until 1965) alu-
minium conductors steel reinforced (ACSR) again with
small cross-section were used (AC-95, 120 and 185 mm 2 ).
From 1965 on only two standard types of ACSR conductors
were adopted -ACO-400 mm 2 and AC- 185 mm 2 . Standard
designs were developed for steel-lattice towers for single
and double circuits with conductors AC- 150, 185, 240 and
300 mm 2 which were used until 1974.

The single circuit tower horizontal configuration initially
adopted in the 220 kV overhead transmission lines were
replaced by guyed portal towers. Later on, the first 400 kV
overhead transmission lines were built with similar types
of towers.

Further on, bolt type steel lattice towers for single and
double circuits were applied.

An important point in the overhead transmission lines
construction was the effort to use double circuit lines with
a view to cutting down the time and volume of construc-
tion works, as well as to protect agricultural lands.

By 1970 the following substations were built:

• Nine 220 kV substations -3020 MVA installed capacity;

• One hundred and thirty 110/10-20 kV substations-
5213 MVA installed capacity.

The 110 kV system had 110/20 distribution substations
(also 110/10 kV in some of the larger towns) with two on-
load tap changers. The first substations of that type desig-
ned and constructed by Bulgarian engineers were equipped
with imported low-oil and air-blast circuit breakers until
1951. From that year on Bulgarian low-oil circuit breakers
and disconnectors were applied. The 5.6 MVA transformer
capacities used initially were gradually replaced by 20, 40
and 63 MVA, the last two -with tapped windings. Most of
the 110 kV power transformers were made in Bulgaria.
The substations had a double-bus system at the 10-20 kV
side. The 220/110 kV substations were built with single-
bus or double-bus systems, the unit power of their trans-
formers reaching 200 MVA. Their transformers were also
on-load regulated. After 1973-1974 glass insulators were
used in all substations and transmission lines.

For the medium-voltage networks in 1954 started the pro-
duction of hollow centrifugal 12-meter poles types "300"
and "500" for single and double circuits for conductors
M-25, M-35 and M-50. These poles replaced the vibrated-
concrete poles cast on site, used till that time. Later on,
13-meter poles were introduced. With the application of
aluminium-steel conductors, new reinforced-concrete and

steel-lattice towers were developed for single and double
circuits for conductors -AC-50, AC-70, and AC-95 mm 2 .

With the nationalization of electrification, the green light

was also given to rural electrification which was under-
developed during the first half of the 20th century.

For the purpose, a specialized Regional Electrical Projects
Directorate was established with Energohydroproject with 12
branch offices in the country for the respective electrifica-
tion regions and one department "Urban Electrical
Networks" for Sofia and for the general electricity supply
plans for all towns and holiday resorts in the country (1952).

The Regional Electrical Projects Directorate set all the
designs of town and regional electrical networks on a sci-
entific basis, by developing and applying new and appro-
priate methods and guidelines. The constant growth of
electrical loads reaching 10 MW/km 2 , and even 20 MW/km 2
in perspective, necessitated "deep" HV penetration in the
large cities through 110 kV transmission lines for
110/10-20 kV substations. The large industrial works also
adopted 110 kV power supply.

The development of the electrification system in Bulgaria
necessitated the construction of an interconnection line
with Romania at the very beginning of the period reviewed
here. For the purpose, a 60 kV underground cable line
Rousse-Giurgiu was laid across the Danube in 1950.

In addition, two 110 kV interconnections with Yugoslavia
were built: Breznik Substation -Varla HPP (1961), and
Kula Substation -Vrashka Chuka Substation (1964). At the
same time, in 1960 the East-European countries Hungary,
East Germany, Poland and Czechoslovakia signed an
agreement for interconnecting their power systems for a
parallel operation (1960).

From 1962 on the East-European countries- members of the
COMECON, including Bulgaria, established tfie Interconnec-
ted Power System for parallel operation and coordination
of the planned-mode on-line control between the different
dispatching centers. In 1967, a 220 kV interconnection line
with Romania-Boichinovtsi-Kraiova was commissioned.
Later on it was redirected to connect theKozlodur nuclear
power plant and Kraiova. By the end of the period reviewed
here, the electric power supply provided by the electric

power systems of the Interconnected Power System reached
13 billion kWh (1970).

Table 9 presents a summary of the overall electric power
network development in Bulgaria within the period
reviewed here.

nterconr

I i'Ctr i i i i i j n s^liim

t>j elect rifle a 1 1 cBtBl:. the ^fi|iHill>itTy; : mUMB^- 1 Wi

Tab]e 9: Length of the electric power network (km)

750 kV 400 k V

220 kV

:' Mhilml

1HTT

OHTl

V/ 1. 1 i Ju

I U lai

OHTI

vJlll L

Total OHTL

fable

1 \J Ldl

1948 —

—

602*

9062

—

9 062

14 605

1950 —

- 396

1 146*

12127

12 127

19 286

1955 —

1 134

2 088*

17 825

24 833

1960 -

329 2 442

3 447*

25 087

35143

1965 —

| 821 3 655

4 758*

29 734

40 881

1 576

42 457

1970

1741 4 975

5 493

33 489

3 157

36 646

44 780

3 894

48 674

including 60 IV and 35 kV networks

for the period 1948-1960, including a minor length of cable lines

Thus, for a period of 22 years the 35-220 kV overhead
transmission lines increased 12 fold, the medium voltage
networks-4 fold, and the low-voltage networks-3,3 fold
which indices show a rapid development of electrifica-
tion in Bulgaria.

With respect to the relay protection used, it should be
noted that 3 -zone distance protections were used against
all kinds of short circuits in the 110 kV networks, and
three-stage directional earth fault protections -as backup.
Short overhead transmission lines used mainly differen-
tial protections. Three-phase automatic reclosing (ARC)
was applied. The busbar differential protections were
normally used at the 110 kV substations with single-section
and double busbars.

In the 220 kV networks, the main protections were 3-zone
distance protections, and the back-up ones were four-
stage, directional earth fault protections. In some cases,
differential protections with a cable connection, or differ-
ential-phase HF protections were applied. The automatic
reclosing devices permitted application of single-phase or
quick three-phase tripping. The busbars in the 220 kV
substations were fitted with differential protections and
circuit breaker failure backup.

Emergency automation was implemented by means of
automatic frequency load shedding systems, automatic
frequency isolation of power plants in an independent
region, decentralized load shedding automatic devices in
cases of transformer overloading, automatic dividing
devices for short-circuit current limiting and automatic
dividing devices for interconnection transmission line
overloading and asynchronous operation.

The reactive electrical loads were compensated by low
and medium voltage static capacitor banks.

3.3. Electricity Demand

During the period reviewed here, the electricity demand
and the maximum load of the electrification system
significantly increased as evident from Table 10.

Table 10: Gross electricity demand and maximum load

of the electrification system

Electric power

kWh

Annual

kWh

per capita

oad, MW

1945

401

57.8

1950

819

15.4

112.6

113

1955

2 106

20.8

281

346

1960

4 685

17.3

596

808

1965

10 232

16.9

1 246

1 591

1970

19 407

13.7

2 286

3 295

There was a high annual rate of electricity consumption.
In the sixties it grew 3-6 times faster than the national
income.

Table 11 presents the structure of electricity consumption.
It shows that the industry occupied the largest share of
it-49.7-f58.8°/o, and the share of public service demand con-
stituted 24.7°/o of the gross electricity consumption and that
percent rate gradually decreased reaching 17.4% in 1970.

Table 11 : Electricity consumption by consumer categories (kWhx 10 6 )

Industry

1952
1955
1960
1965

686

1 055

2 491
5 555

1970 11 550

ran sport
Communi
cation

2.1
52
96
253
404

Agri-
culture

7
70
164
455
691

«: -

Ci'/il

Public Lit i

lity Sector

Cons-
truction

Total

Household

341

135

390

206

906

530

135

2 054

1 180

272

3 405

2 595

Auxiliary

tion

rans- Total
mission Con sump
Losses tion

114
166
317
1 047
1 636

206
312
637
786
1 448

1 379

2 106
4 685

10 285
19 616

That was mainly due to the increased share of industry,
mainly due to the high energy-intensive character of
metallurgical and chemical industries (Table 12).

Table 12; Relative electricity consumption by branches of industry (°/o)

Heating

5.6

7.4

11.1

Metallurgy

10.<

22.2

25.6

25.9

Machine Building

12.<

13.1

9.6

Chemical Industry

24.

20.3

27.2

26.6

Production of materials

for civil works

10.

8.8

7.1

6.3

Light and Food Processing

Industry

22.8

14.9

13.5

Others

7.2

8.3

7.6

'ni l'' * i "' •■ ■ ' -

TOTAL in million kWh

1 055

2 491

5 555

10 735

The other economic branches, such as transport, commu-
nications, agriculture and construction, had a small share
in electricity consumption. The Bulgarian railways elec-
trification started in 1963 and all main railways were
electrified during the years that followed.

It is worth noting that by the end of the period reviewed
(1970) all settlements in the country had been electrified.
5298 population centers (93.9%), giving residence to 99.6%
of the Bulgarian population, were electrified.

In terms of operation, at the beginning of the fifties a dis-
patching service was created. Over the years that fol-
lowed, it developed at three levels: National Dispatching
Center in Sofia, regional dispatching centers (Sofia,
Plovdiv and Gorna Oryahovitsa), and district dispatching
units at the electricity supply enterprises and their
branches. An automatic dispatching service and a
telecommunication system covered 35 of the most impor-
tant sites. Automatic frequency control system and
exchange capacity control system were modeled.

By 1970, with the overall electrification of the country,
the daily load curve of the electrification system consid-
erably changed by seasons and time of the day.

The ratio between maximum and minimum loads signifi-
cantly increased. In December 1970 the average monthly
load minimum was 48°/o of the maximum, and the average
annual load was about 40%. That necessitated the con-
struction of load-following power plants, including
pumped-storage hydro power plants.

2 4 6 8 10 12 14 16 18 20 22 24 2 4 6 8 10 12 14 15 18 20 22 24

August Time (hrs.) of the day December Time(hrs-) of the day

Fig. 1 4 1 Load curves on typical days in August and December 1 971

Ent

lectrificat

ion iof the Goi;

1379

352

686

21239

19616

Fig. 15: Pattern of the gross electricity consumpt

in Bulgaria, 1952-1971

17521

1597

513
Ml

1771

2106

2420

Industry
Public sector
Other consumers

4-685

3895

2 670

3040

6133

54-50

1631

1441

1164

1013

3336

2996

1961 '

1962

7278

1948

1409

3921

15790

13788

11811

10285

8706

1962

6786

7798

4288

8795

10273

11550

11994

1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971

During the reviewed period 1948-1970 the electrification
in Bulgaria developed at a considerably high rate thanks
to the following four main factors:

1. Nationalization of electrification.

2. Increasing the number of graduates of the State Tech-
nical University- engineers and architects of all specialties,
as well as opening of technical schools for technicians
training.

3. Faster development of national electrical industry in
order to meet the requirements of the country and exports
to other countries.

4. Establishment of Energoproject in 1948 - research
institute of project investigations and engineering design.
This institute became the center for training experts not
only for the Bulgarian electrification, but for project
engineering and construction abroad, as well. A number
of other specialized research institutes also appeared in
that field, closely connected with electrification, such as
the Research and Design Institute of Electrical Industry,
Techenergo.

I ni rod u c t io mp f new Technologies in I lectrification 19 /1-1991

The National Dispatching
Center of Sofia

he 20-year period of developing an electric
power system in Bulgaria (1971-1991)
reviewed in this chapter was notable for the
introduction of significant scientific and techno-
logical achievements in the three main sections
of the electrification system: electric power gener-
ation, transmission and distribution.

Large public utility thermal power plants and district
heating plants were constructed, as well as the nuclear
power plant (NPP) at Kozloduy (Table 13).

Table 13: Public utility thermal power plants 1971-1991

Plant name

Year of

commissi-
oning

Installed capacity, MW

Fuel

1st stage

Extension

Total

type

Bobov Dol

1973

210

2x210

630

brown coal

Maritsa East-3

1978

210

3x210

840

lignite coal

In parallel with the large thermal power plants, a number
of smaller district heating plants were built in the larger
cities (Plovdiv, Rousse, Pleven, etc.) Their capacity was
usually several tens of megawatts with the exception of
Plovdiv-North TPP (60 MW).

Bobov Dol TPP

commissioned in 1975
front view

The Bel me ken Dam

constructed in 1974

The Belmeken PSHPP

Machine Hall

In the field of hydro-electric power, after a number of proj-
ect studies that started in the 1960's, the largest Bulgarian
hydro-power cascades were constructed, as follows:

❖

Dospat-Vacha with total capacity of 401 MW
(1972-1984);

Belmeken-Sestrimo with total capacity of 1599 MW
(1974-1995).

Table 6 shows the main technical indices of the two
hydro-electric cascades and the individual power plants
attached to them, as well as the year of their commis-
sioning. At two of these power plants there are pump-
storage sets (Antonivanovtsi and Belmeken), while Chaira
is a purely pumped-storage power plant of a very high
capacity (854 MW, and 760 MW in the pumping mode).

It is worth mentioning that the Chaira Pumped -Storage
Power Plant is unique in terms of its installed capacity
and other technical parameters, and is called the "Pearl"
of the Bulgarian Hydro-Electric Engine erin;

The two cascades together have been designed to gener-
ate 3211. 10 5 kWh, and the overall annual utilization ratio
of their installed capacities is relatively low (T=1600 h).
Both cascades were built in the Rila-Rhodopes with
numerous long headrace tunnels with covered culverts.
It should be noted that many of the machines in these
plants (pumps, generators), as well as the hydraulic facilities
were products of Bulgarian industry.

■

Introduction of new Techno!

n Electrification 197

DOSPAT-VACHA Hydro-Power Cascade

commissioned between 1958 and 1965

Dospcrt Dam

: ': : : ': *

TestelHPP

The Dospat Dam

fflnmaMSi-,

1S0QQDD DerinHPP

fesfoe/ Compensation Basin

fes/ie/ HPP

Machine Hall

Antonivanovtsi Dam 8 HPP-PSHPP

... .

Krichim Dam

Krichim HPP-PSHPP

Vacha HPP

Devin HPP

general view

Krichim (Antonivanovtsi) Dam

The Krichim Dam

spillway and
110 kV switchyard

The Kozloduy NPP

the WOO MW unit machine hall

During this period the Kozloduy nuclear power plant was
constructed and commissioned on the Danube (1974).
Its initial capacity consisted of 2x440 MW WER-440
reactors. Later on it was extended by another 2x440 MW
reactors of the same type. In 1987 Unit 5, WER-1000
with a capacity of 1000 MW was commissioned, and in
1991 -Unit 6 of the same type. Thus the total capacity of
Kozloduy amounted to 1760+2000 = 3760 MW. Its annual
output is presented in Table 14.

During the period reviewed here, the electric power gen-
erated by Kozloduy NPP reached 35.6°/o of the total power
generated in the country (1989), and in the recent years
its share has exceeded 40%.

Table 14: Electric Power Generated by Kozloduy NPP, kWh.10 6

Power

Kozloduy NPP Generated in

the country

Share
of the NPP

1975

2 550

25 273

10.1

1980

6 165

34 833

17.7

1985

13 131

41 632

31.5

1988

16 030

45 021

35.6

1989

14 565

44 259

32.9

1990

14 655

42 130

34.8

1995

17 261

42 003

41.1

1996

18 082

42 801

42.2

I mrodtfctioli tif new Technologies in Electrification 1971*199f

The construction of a second nuclear power plant also
was begun on the Danube-Belene NPP. However, after
considerable progress of the construction, it was stopped
and has not been continued.

The 220 kV overhead transmission line ring:
Aleko-Maritsa East-Dobrudja-Gorna Oryahovitsa-Aleko
was completed in 1971.

During that period a 400 kV transmission network was
constructed -comparatively big for the scale of Bulgaria.
It was developed according to the "closed loop" pattern,
like the 220 kV and 110 kV networks, and was completed
in 1984. At the same time, interconnection lines for such
voltages were also built with the countries listed below:

Soviet Union (Moldova)

400 kV

(1972) and with Romania

Soviet Union (the Ukraine)

750 kV

|' ' ' . i. 1 Li r. i ii i * 1' ■ V. — — ■ ' * ■■ ■• - ' ■ .-. ' ■■•

(1987) and with Romania

Romania

400 kV

(1986) from Kozloduy NPP

Turkey

400 kV

(1975)

Greece

400 kV

(1988)

Serbia

110 kV

(1961, 1964)

400 kV

(1975)

Macedonia

110 kV

(1980)

400 kV

(planned for 1999)

The Kozloduy NPP

Control Room

m m m ■ District bounda ries

Regional Power system
boundaries
District center

Fig. 1 6: District and boundaries of the regional power system in Bulgaria, 1 96ft

Introduction of new Technologies in Electrification 1971-1991

——————

7. Varna TPP, commissioned in 1969-overaH view

2. Varna Substation 750/400 W, commissioned in 1987

3. Varna Substation 750/400 kV~ transformer area

4. Varna Substation 750/400 kV- 750 kV switchyard

The related power supply substations for 220, 400 and
750 kV were also constructed, as well as a considerable
number of substations for 110/10-20 kV (Table 15).

Table 15: Number and capacities of substations and transformers

(not including those at the plant sites)

Substations ft
transformers

■

S/s 750/400 kV

pes.

Transf. 750/400 kV

MVA

—

2 500*

S/s 400/220/110 kV

pes.

Transf. 400/220 kV

MVA

1 260

1 890

Transf. 400/110 kV

MVA

250

500

1 000

1000

1 000

Transf. 220/110 kV

MVA

800

1 000

1 400

S/s 400/110 kV

pes.

Transf. 400/110 kV

MVA

500

1 500

2 500

2 900

S/s 220/110 kV

pes.

Transf. 220/110 kV

MVA

800

1 600

3 020

4 420

5 200

5 660

6 860

8 860

S/s 110/10-20 kV

pes.

130

186

283

406

442

451

Transf. 110/10-20kV

MVA

2 600

3 640

5213

7 982

12412

19 833

22 880

23 571

* two 1250 MVA banks (6 single-phase transformers)

110/10 kV Geo Milev Substation (Softa) 400/1 10 W Sofia- West Substation

with W0kVSF 6 metal clad switchgear, commissioned in 1984 commissioned in 1981

Introduction of new Technologies in Electrification 1971-1991

■ ■

■

400 kV overhead transmission fine

steel lattice pottal tower

220 kV overhead transmission line

guyed steel lattice towers

400 kV overhead transmission line

double eifCLfit lattice tower

400 kV overhead transmission line
220 kV overhead transmission line
Q Substation

Fig. 17: Diagram of the 400 kVand 220 kV transmission system in Bulgaria, 1980

31.60/0

Fig. 18:

Electric power loses in
transmission, transformation
and distribution. 1980

9.4o/o

7.70/0

19.70/0

16.3 0/0

1 5.3 0/0

110 kV overhead transmission lines
220 kV overhead transmission lines
400 kV overhead transmission lines
380/220 V overhead transmission lines
Transformer units
20 kV transmission lines and

20 kV underground cable

During this period significant improvements were intro-
duced in the primary and secondary switching technology
of large 220, 400 and 750 kV supply substations. Up-to-date
relay protection and automation were used.

High-voltage (110 kV) "deep penetration" was applied in
the central regions of the large cities: Sofia, Plovdiv,
Varna and Rousse, with a view to managing the larger
electrical loads. For the purpose, 110 kV oil-filled cables
were used, as well as dry cables with polyethylene insu-
lation. 110/10-20 kV substations were built, with 110 kV
metal-clad switchgears and SFe insulation.

The cables used in MV and LV distribution networks had
polyethylene insulation and PVC insulation.

By means of the 220 kV, 400 kV and 750 kV intercon-
nection lines Bulgaria joined the Interconnected Power
System of the East European countries controlled by the
Dispatching Center in Prague.

Table 16 presents the development of electricity demand
by economic branches for the period 1970-1989.

Table 16: Development of electricity demand in various branches

of the economy (1970-1989)

Demand

mln. kWh

19 406 28 860

38 665

45 925 49 167 48 675

Industry

59.9 51.4

46.1

43.6 43.1 42.18

Civil construction

o/o

1.4 1.5

2.6

2.5 2.3 2.04

Transport 8t communications

o/o

2.1 2.8

2.9

2.9 3.0 3.10

Agriculture

o/o

3 1 5 3 1 3

2.8

2.4 2.2 2.41

Public utility sector

o/o

17.4 22.4

27.3

30.0 29.6 30.75

Households

o/o

17.7

20.8 20.2 20.92

Transmission

o/o

7.4 8.3

8.9

8.7 9.6 9.57

Auxiliary consumption

o/o

8.3 10.3

9.4

Introduction of new Tec hndlotfies in Electrific

)n 1971-19S

During the period reviewed here the share of industrial
electricity demand decreased. This was due to the delayed
construction of new energy-intensive industrial enterprises
such as metallurgical and chemical works. On the other
hand, the share of public service demand increased but
was still low compared to that in the developed countries.

Fig. 1 9 : Electricity supply system of Sofia (1978)

A, For the period until 2000,implemented 1985

Geo Milev
110/10 kV

B. A concept of transition from "main line
to "radial"- type network after 2000

Kourilo
1 1 0/20 kV

Sofia-West
400/110 kV

MCO 400

Bank/a

Moderno
Predgradie

1 10/20 kV

Vrabnitsa
_ 110/20/10 kV

Metro I lliantsi
110/10 kV 110/20 kV

High voltage
Equipment Plant
110/20 kV

Orion

110/20/10 kV

Smirnenski
1 1 0/20 kV

Metro I
110/IOkV

Metal urgic
400/110 kV

Lakprom
110/20 kV

Water Treatment Plant
110/6 kV

G. Benkovski
110/20/10 kV

adost
110/10 kV

Sofia-South
220/110 kV

N. Kolev
110/10 kV

Borimechka
110/10 kV

Sofia TPP
220/110 kV

Maria Louisa
110/10 kV

Vl.Zaimov
110/10 kV

H. Dimitar
110/20/10 kV

Vrazhdebna
11 0/20 kV

"•::?ms

Poduyane
110/10 kV

Stolnik

400/220/ 1 1 kV

West TPP

Suhodol
110/20 kV

0. Dimitrov
110/20/10 kV

Sredets
110/10 kV

Serdika
110/IOkV

Railway Station
110/20 kV

Knyazhevo
110/20/10 kV

Hipodruma
HO/10 kV

Vitosha
110/10 kV

Geo Milev
110/10 kV

Al. Naumov

Industria
110/20 kV

2 ACO 400

Kaziehene
220/110 kV

110/10 kV l1 °/ l0kV

Sofia-East
110/20/10 kV

Pavlovo
110/20 kV

Krasno selo
110/20/10 kV

Boyana
110/10 kV

Student Cam
Pioner 110/20 kV

110/20 kV

2 ACO 400

" Sofia-South

2 AC04QO^~*^V 220/110 kV

O
CN
CM

Mladost
110/10 kV

Computer
Hardware Works
110/10 kV

2 ACO 400

Sofia-East TPP

Cherni Vrah
110/20 kV

Lozen
110/20 kV

2 ACO 400

Gorublyane

Kliment Ohridski
110/20 kV

Legend

110 kV overhead transmission line

110 kV underground cable

Existing substation 220 kV and 400 kV

220 kV and 400 kV Substation -under construction

O 110/10-20 kV Existing substation
O 110/10-20 kV Future substation

Fig. 20: Diagram of the 400, 220 and 110 kV transmission

system in Bulgaria, 1990

I§alnita (Romania)

Vulkane^ti (Moldova)

Zajecar (Yugoslavia)

Vria (Yugoslavia)

Kriva Palanka

Isaccea (Romania)

Strumica (Macedonia)

NPP

7 50 kV overhead transmission line
4-00 k\f overhead transmission line
2 20 kV overhead transmission line
110 kV overhead transmission line
Substation
4-00 kVOHTL under construction

Erection of a 400 kV

overhead transmission line

20 kV steel-lattice tower

transformer

The absolute load maximum was reached in 1989 (12th
December) -833 2 MW, and the absolute load minimum-
3083 MW (on September 5th). The annual utilization ratio
at maximum load was T= 5841 h. The extreme load value
ratio was 0.456 which shows a comparatively good load
curve density.

After 1988 there was a general decrease in electricity
demand due to the decrease of industrial production as
a whole.

Considerable success was achieved in railway transport
electrification covering 2640 km electrified railways in
1990, i.e. 61.4% of their total length. The relative share
of electric traction in the total volume of cargo carriage
reached 82.2%.

20 W overhead distribution line-
steel -lattice tower

DeyliJ^phient of Electrification in the MarRet Economy (after 199

he electrification authority underwent considerable
structural changes after 1989 when a democratic rule
was established in Bulgaria (November 10th 1989).
On January 1st, 1992 a single-owner state-property com-
mercial company-Natsionalna Elektricheska Kompania
(Bulgarian Electric Utility), was set up with the Committee
of Energy, and the local power generation and power sup-
ply enterprises, as well as the investment enterprises
(Integrated Works until then) became subdivisions of the
Bulgarian Electric Utility.

Due to a serious general decline of the Bulgarian industry
as a whole, the generation and consumption of electric
power has also significantly decreased. Household elec-
tricity consumption, however, has retained its level and
even marked a certain growth. Tables 17 and 18 show the
electricity generation and consumption during that period.

Table 1 7 : Installed capacities and electricity generation in Bulgaria

Year

Thermal
Po we r PI a

ro-power
Plants

GWh

H Nuclear
Power Plants

Total

max. load

MW GWh

Mm« ii mini ■iiiiii i m.i ■ him

1945

1950

1955

111

298

231
530

1 425

134

170

267

648

127

176

401
797

2 073

113
346

1960
1965

1970

465
1 357

2 768
8 243

3 264 17 357

460
770

814

1 889

2 005

2 158

4 657

2 127 10 248

808
1 591

4 075 19 515 3 295

1975

1980

4 312 20 230

5 666 24 957

1 720
1 868

2 453

3 713

1 320

2 554
6 165

6 912 25 237

5 200

8 854 34 835 6 922

1985
1988

1990

1995

6 508 26 265

6 574 26 395

6 402 25 624

6 550 22 235

1 975
1 975

1 973

2 440

2 236
2 596

1 851

2 507

1 760 13 131

10 913 41 632

2 760 16 030 11 309 45 021
2 760 14 655 11 135 42 130

3 760 17 261

12 750 42 003

7 878

8 115
8 110
7 522

1997

6 550 22 119

2 872

2 927

3 760 17 751

13 182 42 797

7 232

1998

6 550 21 471

2 872

3 316

3 760 16 899 13 182 41 686 7 257

* including two generating sets at the Chaira pumped-storage hydro-power plant,
still in the process of construction (432/380 MW)

Table 18: Development of electric power generation and its balance (1989-1995)

Measuring
unit

1995

Resources

mln. kWh

265

528

000

38 899

628

349

964

Generation

mln. kWh

44 328

141

917

35 610

998

176

003

Import

rain. kWh

937

387

083

3 289

630

173

961

Export

mln. kWh

548

597

959

584

520

245

121

Net Consumption

Industry

mln. kWh

149

925

173

13 173

353

793

N/A

Households

rain. kWh

183

475

10 405

9 685

10 021

806

956

7 500

7 000

6 500

6 000

5 500

5 000

4500

4000

3 500

3 000

2 500

2 000

1 500

1 000

500

4 000

3 750

3 500

3 250

3 000

2 750

2 500

2 250

2 000

1 750

1 50O

1 250

1 000

750

500

250

4 6

8 10 12 14 16 18

Time (hrs.) of the day

20 22 24

6 8 10 12 14- 1* 18

Time (hrs.) of the day

20 22 24

Load

HPP

TPP

Industrial

NPP

Fig. 21 1 Load curves in MW on typical days-in July [20.07.1994) and in December (21.12.1994-)

BELMEKEIM-SESTRIMO-CHAIRA
Hydro-Power Cascade

commissioned between 1974-1995

Chaira pumped -storage HPP

the indoorswitchgwrand tunnel
with 400 kV cable leads

I Chaira PSHPP

■

BelmekenDam

Chaira Don

VB'." }

ODDDD

Bdmeken HPP

Stankovi Baroki
Compensation Basin

Sestrimo HPP

Daily Compensation Basin

H D DO

Momina Klissoura HPP

/. Belmeken HPP-PSHPP, commissioned in 1974

2. Momina Kiissoura HPP, front view

3. Sestrimo HPP, front view

4. Chaira pumped-storage HPP- machine hall

5. Chaira pumped-storage HPP- the lower compensation basin

6. 400 kV Vetren Nodal Plant

|,| J QR Y o f tl§

l^alnita [Romania]

Vufkane^ti (Moldova)

Zajecar (Yugoslavia)

Vrla (Yugoslavia)

Isaccea (Romania)

Kriva Palanka (Macedonia)

Strumica (Macedonia)

Fig. 22: Diagram of the Bulgarian Electrification System in 1995

m NPP

750 kV overhead transmission line
400 kV overhead transmission line
220 kV overhead transmission line
110 k\/ overhead transmission line
Substation
400 kV OHTL ur-der construction

Fig. 23 ■ Electricity consumption

in Bulgaria, million kWh

35 000

30 000

25 000

20 000

15 000

10 000

5 000

1992 1993 1994 1995 1996 1997

Year

Street lighting

Household

Public utility sector
Industry

Electric power generation and consumption reached their
minimum in 1992 after which there has been quite a
small increase.

The construction of electricity transmission facilities also
declined. The 400 kV connecting line between the Vetren
nodal plant and the Chaira PSHPP was completed in that
period, as well as the 400/110 kV Tsarevets Substation.

An energy development strategy was developed in 1995.
It includes:

❖ up to 2000: urgent measures for stabilization
of the sector;

❖

2001-2010: middle-term forecast envisaging
total electricity consumption of 49 billion kWh
in 2005, and 52-54 billion kWh in 2010;

❖ 2011-2020: long-term forecast, according to which
the expected electricity consumption in Bulgaria
in 2020 should reach 58 billion kWh.

The long-term forecast of electricity consumption in
Bulgaria may be considered as too skeptical, but in the
event of a more favorable general economic development
of the country, that forecast may be significantly exceeded.

Development of E KtJ't f i f i c a t i on in the Mai kci I ic o n <> m y m\'\ er 1991)

7 5O0

7 000

6 5O0

6 0O0

5 500

5 000

4 5O0

4 000

3 5O0

3OO0

2 5O0

2 000

1 5O0

1 0O0

5O0

4750
4 500
4250
4000
3 750
3 500
3250
3000
2750
2500
2250
2000
1750
1 500
1 250
1000
750
500
250

8 10 12 14 16 18 20 22 24

Time (hrs.) of the day

8 10 12 14 16 18 20 22 24

Time (hrs.) of the day

Fig. 24: Load curves on typical days in MW-in July (15.07.1997) and in January (22.01.1997)

20000

18 000

16 000

1 4 000

12 000

10 000

8 000

6 000

4 000

2 000

1992

1993

1994

1995

1996

1997

Year

NPP

TPP local fuel

TPP imported fuel

HPP

Fig. 25: Electricity generated by types of power plants, million kWh

Devel oum eiilME. t h e Em c

c a lj $ jffiai p w e p t l n < i > i s i ry

Before the end of World War II there was no devel-
oped electrical equipment industry in Bulgaria
worth mentioning but just rudiments of it. In
1926, the first asynchronous motors, small dynamos,
transformers, circuit breakers, etc., were manufactured in
a small private workshop. During the thirties, electric
motors up to 7 hp were manufactured in small private
workshops. In 1934 the manufacture of electrical bulbs
was started in Sliven in a workshop employing 20 work-
ers. And in 1935, a workshop manufacturing components
for internal electrical installations was opened in Rousse.

■

Transformer production in Bulgaria also began at that
time- in 1934, when the first oil transformers with 320 kVA
average capacity were designed for the purposes of elec-
trification.

Manufacture of insulated copper conductors started in
1932 in Sevlievo and during World War II such work-
shops were opened in Bourgas, as well.

All these small workshops were the beginning of future
large factories and works which would be developed as
state enterprises during the second half of the 20th cen-
tury. They met the needs of the country for electrical
products and some were exported, too. Initially such
enterprises were transformed into factories united in an
Electrical Industry Syndicate (1947). After the nationaiza-
tion of industry in 1948 this syndicate was re-organized
and turned into a state group -"Elprorn" with the Ministry
of Electrification and Amelioration. Elprorn undertook the
construction of several basic works and, in the first place,
the High Voltage Equipment Works in Sofia. Three of the
factories already existing in the city-for electric motors,
for transformers and apparatuses, were moved into the new
buildings of the works in 1949.

Many people would find it quite a strange idea to con-
struct such huge works with workshops disposed on an
area of 15 000 m 2 as was the case with the High Voltage
Equipment Works in Sofia. However, the organizing talent
and foresight of its founders led to its implementation.

The Soviet Union sent the first machines and experienced
specialists who rendered significant assistance. At the
same time the electrical company Ganz- Budapest became
a patron of the High Voltage Equipment Works and com-
missioned its engineers to render help. The company
provided a 3-year training course of Bulgarian experts
in Budapest.

As the various product lines grew and expanded, the
High Voltage Equipment Works split up into a number of
new electrical works such as: Electrical Apparatus Works -
Plovdiv; Elevator Factory- Sofia (1964); Iskra Works -
Sofia for manufacture of manual low-voltage devices;
Elprom Works-Varna for electrical household appliances
and heaters, Lighting Fixtures Works in Stara Zagora.

Separate DC Equipment Works were built in Sofia in
1960. Besides, new works for electric motors were built
in Troyan and Plovdiv, and mini-electric motor works-
in Lovech and Teteven.

Transformer department

at the High Voltage Equipment

Works in Sofia

Dpijfelo p nfMjll of the ElectflffiiJ gquipniei

High Voltage Equipment Works in Sofia
the test laboratory

Thus, in 1967, the Elprom Group included 20 works, one
research institute and 6 technological development
centers at some of the works. And while in 1947 the
Bulgarian electrical equipment industry met only 0.65%
of the needs of the country, in 1967 it met already more
than 90°/o of the demand, and constituted about 20°/o of
the total machine building in the country.

Electric motors are among the most important items in
the production range of the High Voltage Equipment
Works in Sofia. The Works recruited young electrical
engineers among the first graduates of the State Technical
University many of whom were holders of bursaries from
Elprom. Young and ambitious, they joined the older and
more experienced engineers in the fulfillment of the
Works Programs. Later on, many of these engineers
became ranking decision makers, highly qualified teach-
ers, scientists, designers and technologists.

High Voltage
Equipment Works

in Sofia -
the test laboratory

As early as 1949, a package of technical documentation
on a new developed series of general-purpose asynch-
ronous low-voltage electric motors types "A" and "AO" of
10 kW or less for direct connection to the mains was
received from the Soviet Union. With a view to the limit-
ed capacity of the Bulgarian electric power system, they
had to be designed for indirect start, i.e. through star-
delta switches. A Bulgarian series of electric motors of a
new design -AM, and later on, AP and AOP, was devel-
oped. The Bulgarian designers developed more powerful
asynchronous motors up to 100 kW (1951-1956).

Within the period 1956-1958 the Bulgarian specialists
created AO electric motors of an ingenious design with
considerably smaller overall dimensions permitting saving
of non-ferrous metals thanks to the better quality of the
materials used, especially the enamel for conductor insu-
lation and the rotor groove size. Thus the weight of the
motors was reduced by about 30°/o. That motor design was
adopted for manufactures from the COMECON- Eastern
Europe.

The Apparatus Factory in Plovdiv which became an inde-
pendent unit in 1952, developed and manufactured
various types of automatic low-voltage circuit breakers,
ballasts for fluorescent lamps, automotive switches and a
number of other related products.

In the early fifties, the first Bulgarian hydro-electric
generators were made: first for Ustovo HPP with 315 kVA
output, 1000 rmp, and soon after that -for Studena HPP-
with 500 kVA output, 1000 rmp, for Batoshevo HPP- with
1000 kVA output, 750 rmp, for Barzia HPP -with 4000
kVA output, 500 rmp, etc.

In 1962, a synchronous generator with 30 000 kVA output
was made for Teshel HPP, then another for Krichim HPP
with output 40 000 kVA, so every next hydro-electric
generator manufactured was more powerful.

High Voltage Equipment

Works in Sofia
synchronous generator

Manufacturing of electric motor collectors

These generators were completed with Bulgarian hydro
turbines made at the specialized works in Pleven. There,
in 1954 three Francis type hydro turbines with a capacity
from 0,32 to 62 MW were produced. In 1967 2x30 MW
Francis turbines were made for Teshel HPP. The manufac-
ture of Pelton turbines with capacity between 1.5 and
130 MW was also mastered. In the period 1952-1970
weie manufactured 71 turbines for 23 projects.

[n the meantime manufacture of other turbine equipment
went on- penstock valves, spherical gate valves. Thus, the
gate facility made for Sestrimo HPP was a penstock valve
with 3.5 m clear opening, and for Momina Klissoura
HPP- a spherical gate valve with 2 m clear opening and
83 t weight.

The Bulgarian transformer production was extremely suc-
cessful. The first transformers made at the High Voltage
Equipment Works in Sofia with 5600 kVA capacity for
20 kV, 35 kV, 60 kV and 110 kV were commissioned in
1951. And in 1957, the first Bulgarian 31 500 kVA, 110 kV
transformer with an on-load tap-changer was produced.

The first 35 kV Yansen on-load tap-changer was manu-
factured in Bulgaria in 1954, and two years later the
manufacture of 110 kV on-load tap-changers was started.
Some Bulgarian inventions were applied in that area. The
first 220 kV, 32 MVA transformer was manufactured in
1962, and a 180 MVA autotransformer-in 1965.

Yansen on-load
tap-changers

The High Voltage Equipment Works in Sofia mastered and
began manufacture of low-oil circuit breakers, discon-
nectors," drives, etc. The first low-oil circuit breaker was
intended for 10 kV. The test results in 1951 were quite
encouraging. Within 3-4 years a series of such 10 kV and
20 kV circuit breakers with rated current range up to
1000 A was implemented. The first 110 kV low-oil circuit
breakers were made in 1956.

Special conical-rotor motors were designed for the
Bulgarian world-level electric hoists.

There was also a successful start in the manufacture of
low-voltage apparatuses for switchgears, relays and devices
for process control, automation and mechanization.

The Specialized Works in Rousse manufactured electrical
installation and insulation materials. Two works in Sevlievo
and Smolyan specialized in the manufacture of low volt-
age installation wires and cables. The Cable Works in
Bourgas developed the manufacture of power and tele-
phone cables. All these works grew up from the former
workshops of the thirties and forties.

Porcelain insulators

at the plant in Nikolaevo-
Stara Zogoia Region

metrical : E q u i p $u n d ti'sfijp

Manufacturing of porcelain insulators

at the plant in Nkofaevo-
Stara Zagora district

The only works for porcelain insulators were constructed
in Nikolaevo, Stara Zagora District They were commis-
sioned in 1951, and by 1967 82% of their production was
intended for export. The works made 110 kV porcelain
insulators, as well as insulators for high-voltage switch-
yards and for low-voltage networks.

The present review can hardly cover the Elprom Group
vast production range manufactured at 20 works during
that period. It is essential to say that the Bulgarian elec-
trical equipment industry, along with and at equal level
with the other branches has contributed a lot to the
industrial image of our country. At the same time, the
achievements in the period 1948 -1970 were in fact accu-
mulation of experience for further, higher achievements
in the electrical equipment industry. After 1959, when the
Ministry of Electrification and Water Resources was closed,
the Elprom Group became subordinated to the Committee
of Industry.

The products of the Bulgarian works from the Elprom
Group won a number of prizes at international fairs and
all that encouraged the research workers and design engi-
neers at these works. Their production was well received
both in the country and abroad.

The High Voltage Equipment Works in Sofia gradually
became large-scale Electrical Equipment Works with the
following main lines of production:

❖

Electrical machines: low-voltage general-purpose
unified-series asynchronous motors, high-voltage
electric motors, unique motors and electric motors
with a special application.

Transformers: power transformers for 110, 220
and 400 kV substations and for distribution net-
works, as well as current and voltage measuring
transformers.

■

The Bulgarian series M and MO asynchronous electric
motors were notable for their high technical, economic,
energy and vibro-acoustic indices, and were awarded gold
medals at the Plovdiv and Leipzig Fairs.

A number of works specially for distribution network
electric motors and transformers were built in Troyan,
Lovech, Kyustendil and Godech.

The Elprom-Belfa Works in Sliven mastered the manufac-
ture of various electric light bulbs with the assistance of
Tungsram- Hungary.

After 1965 Bulgaria became specialized in the manufac-
ture of electric trucks and electric hoists for the Bulgarian
market and for export to the East European countries.
Considerable quantities were also exported to other coun-
tries in the world.

The Bulgarian mini-electric motors made at the Elprom
works in Lovech, Troyan and Teteven, as well as the var-
ious machines equipped with them, have become well
known on the international markets. The Bulgarian elec-
trical equipment industry is also very successful in the
production of electrical drives for machine tools with
numerical program control.

Bulgarian electrical equipment industry has achieved sig-
nificant results also in the sphere of HV switchgear pro-
duction. The range of low-oil circuit breakers type MMO
for Voltage 72.5-245 kV and Rated Current 1250-1600 A
meet the home market demand and considerable quanti-
ties are exported abroad, as well.

Since 1985 "Elprom-Avangard'-Sevlievo has been man-
ufacturing, under the license of the Swedish company
"ACEA" (now incorporated with Brown -Bovery as ABB)
the most advanced SF 6 circuit breakers. They are intend-
ed for Rated Current 2500-4000 A and Breaking Current
40 and 50 kA, mainly for export.

The disconnectors produced by Elprom- indoor and out-
door types, single pole and three pole ones, with or with-

■

out earthing switches, with manual, pneumatic or motor
drive, for current up to 630 A, meet the home market
demand, many are also intended for export.

Development of the Electrical Equipment industry

Manufacture ofdiesel generating sets

At present "Elprom -Thermo" Ltd-Balchik produces dis-
connectors for Voltage 66-132 kV and Rated Current up
to 2000 A, as well as manual drives for outdoor discon-
nectors -up to 145 kV, operating under normal and trop-
ical climatic conditions.

In 1964 a special branch "Cermet materials, special alloys
and contact materials" was established with the Research
Institute of Electrical Industry. In 1970 it became an inde-
pendent institute.

From 1975 on all kinds of electrical equipment produc-

in the Elprom-Energo

tion was brought

together

Integrated Works, and for the purposes of research and
development in that field, an Electric Power Technology
Institute was opened in Sofia. The new group covered a
wide range of rotary electrical machines, power and
measuring transformers, on-load tap-changers, apparatuses
and high-voltage complete devices, as well as electronic
control systems for power generation, transmission and
distribution. They all had a significant share in the invest-
ment development of power sector, machine building,
chemistry, metallurgy and other branches of industry.

Manufacture of bare
AC conductors

for OHTL

mtlml

IV switchboard

After 1974 Bulgaria had ingenious solutions and new
technologies. It became a much sought-after manufactur-
er and exporter of on-load tap-changers for large power
transformers. The annual output of on load tap changers
came up to 2777 pes, 96% of which were exported to
more than 30 countries.

The Bulgarian unified series of high-voltage asynchronous
electric motors of 200-1000 kW capacity created in 1976 -
1980 proved to be very competitive on the international
markets. Powerful electric motors for the nuclear and ther-
mal power plants were developed and manufactured. Five
types of vertical electric motors for the secondary circuit of
the nuclear power plant were introduced in production.
Sixty asynchronous electric motors with 250, 500, 1000
and 1600 kW and double-speed motors with 800/400 kW
capacity were manufactured for the Bulgarian nuclear
power plant (1983-1988).

In the period after 1980 for the purposes of nuclear power
production appeared a series of synchronous electric
motors with static excitation system and automatic exci-
tation control within the range 250-1600 kW.

The summit of electric power industry in Bulgaria has been
marked by the adoption of motor-generator units-a new
production technology together with the Japanese company
Toshiba for the needs of the Chaira PSHPP. The reversible
motor-generator units are 240 MW, 19 kV, 600 rpin and are
among the most complex electrical machines at that time.

Motor-generator unit

in the machine hall
of Chairc PSHPP

Diesel generating sets

Within the period 1970-1980 the overall output of the
electrical equipment industry increased about 3 times
(Fig. 26]

292

Fig. 26: Growth

lectrical equipment
industry output (index 1970=100), %

1948

'&7

'60

'65

'7576 7778 '79 '80 '81 Years

On the basis of expanded production capacities and their
intensive utilization, the output of some main groups of
electrical products was significantly increased (Table 19).

Table 19: Output of some main groups of electrical industry products

Branch/Year

Measuring unit

1970

1980

1988

Electric generators

pes

515

1 414

1 694

thousands kW

37.0

32.5

70.9

Electric motors

thousands pes

750.5

947.3

1 251.4

1 401.3

1 890.7

thousands kW

4 194

5 117

7 111

6 652

6 111

Power transformers

pes

4 807

6 179

7 645

9 357

18 281

thousands kVA

3 256

3 924

4 136

4 744

4 472

Generating sets

pes

368

1 163

1 450

3 129

3 772

2 455

26 746

48 516

80 000

126 400

Cables

i *

thousands m

24 030

40 701

56 016

68 698

66 213

Electric washing

machines

• -

pes

56 342

73 321

64580

1 55 900

168 900

Table 20:

Table 20 presents the development of the two main
groups of electrical products typical of that industry.

1939

1948

1950

1956

1960

1965

1970

1975

1980

1985

1988

Electric Motor Production

pes x 10 3

3.0

14.2

122.7

236.0

497.1

750.5

947.3

1 251.4

1 403.3

1 890.7

kWx10 3

105

919

2 864

4 194

5 117

7 111

6 652

6 111

Power Transformer Production

pes

187

860

907

3 924

4 224

4 807

6 179

7 645

9 357

18 281

kVAxlO 3

160

427

1 172

2 672

3 256

3 924

4 135

4 744

4 472

Various
lighting
fixtures

Development of the Electrical Equipment Industr

The wide product range of the Bulgarian electrical equip-
ment industry has had a constant and steady development
in terms of quantity and quality and has found a good
acceptance on the international markets.

After 1989 when democratic rule replaced totalitarian rule,
a structural reform has been carried out in the industry,
including the electrical industry. The reform consists of
privatization of the industrial enterprises which used to
be a state property before that. All that has led to a cer-
tain decrease in the electrical industry output which has
affected its international markets, quite well developed
until then.

Electrical installation components

'■it ■

r«-

•

w ■

Various

household

appliances

% « » » * * • m # « «• « * « « «

Design and Fulfillment of Electric Projects Abroad

As already mentioned, the steady growth of elec-
trification in Bulgaria in the second half of the
20th century also had a great impact on the
design and fulfillment of electric power projects abroad.
The beginning was laid in 1960 with the establishing of
Electroimpex as a foreign-trade enterprise with exclusive
rights in Bulgaria on the import and export of electrical
goods and equipment. In the first years Electroimpex
established business relations with companies from 16
countries in the world. From the very beginning of its
existence Electroimpex was involved in and contributed
with its specialization to the development of the electric
power system, as well as to the establishment of the elec-
trical industry in Bulgaria. The efforts were directed to
overall co-operation and participation in laying the foun-
dations and the development of a market-oriented elec-
trical industry on the basis of full compliance with the
requirements and recommendations of IEC and the most
widely applied international standards such as BS, DIN,
etc. As a result of the efforts made jointly with the man-
ufacturers, Bulgarian electrical goods and equipment
found their place on the international markets.

220 kVHurgada
Substation-
Egypt

Thanks to its own policy and the development of the
Bulgarian electrical industry, a few years after its estab-
lishment the company began to offer engineering services,
as well. At that time they consisted mainly in the organ-
ization of complete projects performed by specialized
Bulgarian subcontractors. During that period, in parallel
with the projects performed, Electroimpex acquired the
potential, experience and reputation of a company famous
in the field of engineering activities.

Design work for 66/1 1 kV Hurgada Substation

Setting of secondary
commutation-Egypt

In 1990 Electroimpex was transformed into a public lim-
ited company the founders of which included Bulgarian
manufacturers of major electrical equipment, research
and design institutes, banks, etc. In 1999 the company
was privatized through Sofia Stock Exchange.

Constructbn of
63J20 kV Bastam
Substation- 1 ran

100

DMign and Fulfil In; en i of kU'cnic Projects A!m

732 kV Overhead transmission line- Kuwait

Today Electro inipex, with its 210 employees in the head
offi.ee, independently performs engineering activities in the
field of electric power projects: design, supply, installation,
adjusting tests, commissioning, supervision, guarantee
and post-guarantee services. On the basis of its own
potential of engineers, economists and other highly qual-
ified specialists, equipment and facilities, the company
provides, by its own efforts, up to 35°/o of the complete
engineering product of the carried out projects for elec-
tric power generation, transmission and distribution. It is
in projects of that type only that the facilities are offered
by Bulgarian and foreign subcontractors in strict confor-
mity with the customers' requirements and the respective
tender documents. Some of the best known manufacturers
such as ABB, Alstom, General Electric, Schneider Electric,
Siemens, etc. appear in Electroimpex List of Approved
Suppliers.

••••• nt&mim&M&i&tjt

66 kV Overhead transmission line
Sour Substation -South Lebanon

101

Indoor 66/1 1 kV, 3x25 MVA

Nadi El Remaya Substation-Egypt

66 kV overhead transmission lines

Saida Substation-lebanon

Electroimpex is awarded a Certificate of
Approval by Bureau Veritas Quality
International in compliance with Quality
Standards BS EN ISO 9001:1994

in the field of engineering services for complete turnkey
electric power projects, including: HV substations, HV
overhead transmission lines, distribution overhead and
cable networks, rural and urban electrification, hydro
power plants, irrigation and water supply pump stations,
package potable water treatment stations, technological
lines and factories for electrical goods manufacturing.

The company is also included in the DG1A Central
Consultancy Register of the European Community.

102

I IT

D esi gn and Pii 1 fill tnent of Electric P r oj ect s Abro ad

Transportation of 220 kV

transformer to Egypt

Electroimpex is well known in more than 85 countries in
Asia, Africa, Europe and South America and in some of
them, such as Germany, UK, France, Italy, Greece,
Albania, Russia, Ukraine, Egypt, Syria, Iraq, Nigeria,
Afghanistan, Lebanon, Jordan, Iran, Pakistan, Nicaragua,
Cuba, Peru, etc., it has established business contacts with
firms with a wide range of activities on the basis of joint-
ventures, agencies or traditionally maintained coopera-
tion contacts.

The company has implemented contracts with 18 coun-
tries in the world for about 100 projects worth more than
500 million USD and has become a well-known and wel-
come partner on the international markets.

The analysis of the financial condition of the company
performed in conformity with the international auditing
standards by the auditor firm KPMG show that
Electroimpex is a successful company with stable eco-
nomic indices, typical of which is 60 mln. USD annual
turnover for the period 1992-1998.

All these facts and figures show
that Bulgaria has significant
achievements and experience
obtained in the process of
construction of a number
of turnkey power projects
abroad which is a warrant for
stable and reliable partnership
with foreign companies.

103

Year of
completion

Value of
completed
projects in

USD'000

ALBANIA

Two 35/10 kV, 2x10 MVA Substations

Supply of complete equipment and materials
for Medium Voltage Distribution Network

1979

1993

2 700

5 000

AFGHANISTAN

* KANDAHAR 110/20 kV, 2x25 MVA Substations

* Twelve 110/20 kV, 1x4 MVA Substations

• DJANGLAG 15/6 kV, 2x2 MVA Substation

• 110 kV, 10 km Overhead Transmission Line

• 20 kV, 300 km Distribution Network

* 660 km Low Voltage Distribution Network

1985
1985
1985
1987
1987
1991

3 400
9 000
1 500

4 700
1 200
1 400

BANGLADESH

• CHITAGONG 33/11 kV, 2x5 MVA Substation

* M0NGLA 33/11 kV, 2x5 MVA Substation

1980
1985

680
640

CHINA

Thirty mini Hydro Power Plants with capacity 2 MW

1961

24 000

CUBA

m Fifty Irrigation Pump Stations
* 33/6 kV, 2x10 MVA Substation

1988
1988

45 000
1 800

EGYPT

* EDFU 132/33/6 kV, 4x40 MVA Substation

* EL SUEZ Petroleum Industries 66/11 kV, 4x25 MVA Substation

* HELWAN UMVERSITY 66/11 kV, 3x25 MVA Substation

* EL M0KATTAM 66/11 kV, 3x25 MVA Substation

* EL MAADI 66/11 kV, 3x25 M VA Substation

* ESKAN EL DOBBAT 66/11 kV, 3x25 MVA Substation

* EL ISMAELIA 66/11 kV, 4x25 MVA Substation

* EL DAWAGEN 66/11 kV, 3x25 MVA Substation

1980
1995
1996
1996
1996
1996
1996
1996

8 500
4 800
3 500
3 500
3 950

3 600

4 450
3 400

104

* GEZERT EL DAHAB 66/11 kV, 4x2 5 MVA Substation 1996 4 050

* NAD I EL RE MAYA 66/11 kV, 3x25 MVA Substation 1997 3 500

* PORT FOUAD 66/11 kV, 4x25 MVA Substation 1997 4 000

* ZAHRAA MADENT NASR 66/11 kV, 4x25 MVA Substation 1997 3 600

* SHERATON 56)11 kV, 4x25 MVA Substation 1997 4 300

* MASNAA 20O EL HARBY 66/11 kV, 3x25 MVA Substation 1997 4 200

* EL-AKHMAS 66/11 kV, 2x25 MVA Substation 1998 4 820

* WADY EL-NATROON 66/11 kV 2x25 MVA Substation 1998 4 958
HURGADA 66/11 (22) kV, 6x25 MVA Substation 1998 7 710
EAST QUANTARA 220/66/22 kV 125 MVA Transformers 1998 1 700
BILBEIS EL-BADALA 66/11 kV, 3x25 MVA Substation 1999 5 760

* KARMOUZ 220/66/11 kV, 125 MVA Transformers 1999 1 700

1 999 5 000

1999 5 760

* HURGADA 220 kV Substation

• ABOU GALEB 66/11, 4x25 MVA

IRAN

• Plant for manufacturing of contactors: 400 000 ps. annually 1984 1 500

• 230 kV, 244 km OHTL, Delivery of Steel Lattice Towers for FREC 1991 2 800

• Five 63/20 kV Substations for SREC

1997 6 800

1984 9 000

1985 8 100

IRAQ

• Contract HT-2 5 including:

- BAGHDAD -NAHRAWAN 132 kV 31 km Overhead Transmission Line

- HAMRIN - KHANAKIN 132 kV, 95 km Overhead Transmission Line

- DOHUK-ZAHO 132 kV, 54 km Overhead Transmission Line

• Contract H-39

TAMIM-TO SLUD J A-D OKAN 132 kV, 166 km Overhead Transmission Line

Contract HT-52 including:

- NASIRIA-NASIRIA NORTH 132 kV, 13 km Overhead Transmission Line

- KADISIA-DIWANIA 132 kV, 10 km Overhead Transmission Line

- K AD I S I A - S AMAWA 132 kV, 86 km Overhead Transmission Line

- NADJAF-NADJAF NORTH 132 kV, 10 km Overhead Transmission Line

• 400 kV-4 km, 132 kV-2.5 km Overhead By-pass Interconnections 1987 880
Lighting of Highways R-5 and Crossings 1990 1 600

1987 17 800

JORDAN

* ZARKA IRBID 132 kV, 55 km Overhead Transmission Line 1978 2 100

* PHOSPHATE MINES 60 kV, 23 km Overhead Transmission Line 1978 1 200

* EL HASA 60/6.6 kV, 6.3 MVA Substation 1978 650

* EL ABAID 60/6.6 kV 6.3 MVA Substation 1982 650

* TEFILIA and SHOUBAK rural area 11 kV, 53 km Overhead
Transmission Line and rural area 0.415 kV, 220 km

Distribution Networks 1982 3 750

105

• •••«««•«* #######

KUWAIT

* ABDULA-SAUD 132 kV, 28 km Overhead Transmission Line

• SAUD-WAFRA Nol 33 kV, 30 km Overhead Transmission Line

1974
1977

1 900
800

LEBANON

• BYKFAYA-KSARA 66 kV, 7 km Overhead Transmission Line

• DAMOUR-SAIDA 66 kV, 18 km Overhead Transmission Line

• LEBANON NORTH -SYRIAN BORDER

220 kV, 31 km Overhead Transmission Line

• JAMHUR-BSALIM 150 kV, 11 km Overhead Transmission Line

• SIBLIN 66/15 kV, 2x20 MVA Substation

• JEITA 66/15 kV, 2x20 MVA Substation

• AWALI-BAUSHRIE 66 kV, 6 km Overhead Transmission Line

• BARED-HALBA 66 kV, 11 km Overhead Transmission Line
HALBA 66/15 kV, 2x20 MVA Substation

• HERMEL 66/15 kV, 2x20 MVA Substation

• ZOUK-BSALIM 150 kV, 10 km Overhead Transmission Line

• MAMELTEIN 66/15 kV, 2x20 MVA Substation

• KOBAYAT- HERMEL 66 kV, 25 km Overhead Transmission Line

• Z0UK-JAMH0UR, 150 kV, 17 km Overhead Transmission Line

• BEITEDIN 66/15 kV, 2x20 MVA Substation

• DBAIEH and ASHRAFIEH Water Pump Stations

• ZOUK-BSALIM Overhead Transmission Line 150 kV (reconstruction)

DAM0UR

• AWALI - J AMHUR reconstruction
of 66 kV Overhead Transmission Line

Supply of Steel Lattice Towers for SAID A - Z AHRANI 66 kV 0HTL
Supply of Steel Lattice Towers for SAIDA-MAHUK 66 kV OHTL

1974
1977

1979
1979
1982
1982
1983
1983
1983
1983
1984
1984
1985
1990
1990
1990
1991
1992

1994
1995
1996

150
350

1 000
400

3 200
3 200
500
300

2 900

2 900
400

3 400
500

2 000

3 500
1 000

430
250

120
100
100

MALTA

♦ Plant for manufacturing of electric motors
with capacity over 4 kW and annual production of 50 000 ps

1982

4 000

NICARAGUA

• EL VIEHO 138f24.9 kV, 1x25 MVA Substation

• PUNTE HUETE 138/24.9 kV, 1x15 MVA Substation

• LAS BANDERAS 138/24.9 kV, 1x15 MVA Substation

• MINA EL LIM0N 69/24.9 kV, Lxl5 MVA Substation

• MATEARE 69/24.9 kV, 1x15 MVA Substation

• Workshop for repairs of Distribution Transformers

1985
1985
1985
1985
1985
1986

1 250
950
950
800
800
630

106

NIGERIA

• KANO STATE 33 kV, 354 km Overhead Transmission Line
and 0.41 5 kV, 280 km Distribution Networks

* KADUNA STATE 33 kV, 45 km Overhead Transmission Line
and 0.41 5 kV, 20 km Distribution Networks

• NEPA 33 kV, 2000 km Overhead Transmission Lines;
11 IcV, 1200 km Overhead Transmission Lines
and 0.415 kV, 1700 km Distribution Lines

* CROSS RrVER STATE 11 kV, 300 km Overhead Transmission Lines
and 0.415 kV, 650 km Distribution Networks

• Ten complete training centers and laboratories for colleges

* Complete electrification of Zones E and F-Abuja includin
33 kV, 11 kV, 0.415 kV Cable Networks, Automatic Traffic

Control System, Street Lighting and Emergency Call and Alarm System,
ABUJA zone E 33/11 kV, 2x15 MVA, Substation
ABUJA zone F 33/11 kV, 2x15 MVA Substation

1984

1985

1986
1986

1992

17 000

4 000

50 000

24 000
10 000

14 800

PAKISTAN

» Seven 66/11 kV, 5 MVA Substations for WAPDA

• Three 66/11 kV, 7.5 MVA Substations for WAPDA

• Six 66/11 kV, 10 MVA Substations for WAPDA

• Vacuum Drying Installations for Power and Distribution Transformers

1970
1972
1973
1973

2 100
1 200

3 000
800

RUSSIA

* Eighteen Complete Medical Centers

• Twenty-five Complete Irrigation Pump Stations

1987
1988

5 400
15 000

SYRIA

• HAMA 66/6.6 kV, 2x12.5 MVA Substation

• H0MS 66/6.6 kV, 2x7.5 MVA Substation

• Plant for manufacturing of Asynchronous Motors

1969
1969
1970

900
900
1 600

VIETNAM

• SH0NG GOT 2 MW (2x1 MW) Hydro Power Plant

• CH1ENG NGAM 2 MW (2x1 MW) Hydro Power Plant

1968
1968

1 000
1 000

107

Written by Assoc. Prof. Mire Spirov, M.Sc. Electrical Engineer

Science editor Alexander Vaklinov, M.Sc. Electrical Engineer
Copy editors Mariana Dotsinska and Zlatka Barakova

Translation by Lyudmila Dimova
Graphic design by Ventsesiav Dyankov ft Roumen Boboshevski
Photography by Avram Avramov and Zhivko Arabov
Photo archival support by Electroimpex pic

Printed in Bulgaria by Obrazovanie ft Nauka

Engineering activities for turnkey electric power projects
according to the requirements of the international standards
Export/import of electrical equipment and goods

Awarded Certificate of Approval by
Bureau Veritas Quality International pursuant to

BS EN1S0 9001:1994

Listed in the European Central Consultancy

1 7, G. Washington Street, 1040 Sofia, BULGARIA, Tel: (+359 2) 86 1 81
Telex: 22959, Fax: (+359 2) 980 0272, E-mail: elimpex@mb.bia-bg.com

' http://www.electroimpex.com

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